War, anarchy, drought and floods have left hundreds of thousands of Somalis in need of aid in one of the world's poorest and most violent countries.

In 2006, relief agencies were hopeful they would be able to send international staff back into the country and increase aid deliveries, after Islamists restored relative calm when they took control of the capital Mogadishu and most of southern Somalia.

But six months later they were defeated by government forces backed by Ethiopian troops, which remained in the country until early 2009.

Since the ousting of Islamists from Mogadishu, tens of thousands have been forced to flee increased violence. An estimated 3.5 million Somalis now need humanitarian aid due to a combination of fighting, displacement and poor harvests.

U.N. officials describe Somalia as the world's worst humanitarian crisis.

Roads have barely been maintained in years, militia and bandits sometimes open fire on convoys, and there are endless roadblocks where gunmen extort money and steal cargoes. Inter-clan fighting is common, making some areas inaccessible. Moving around the country is almost impossible, and Kenya has closed its border citing security fears. However, thousands of Somalis still manage to reach overcrowded refugee camps in Dadaab in northeastern Kenya.

Few international aid staff are posted in Somalia, where foreign workers are a prime target for kidnapping. However, plenty of international relief agencies operate through Somali staff and local partner agencies - although they too are increasingly targeted.

Aid agencies sometimes travel with their own security, but that can also be risky as militia are more likely to ambush them in search of guns and ammunition.

Ninety percent of food aid arrives by sea. But Western warships have had to be deployed to protect the shipments from pirates who prowl off Somalia's lawless coast.

The U.N. Office for the Coordination of Humanitarian Affairs (OCHA) said in 2008 that aid to Somalia had never been so restricted.

The self-declared state of Somaliland, in the north of the country, is relatively safe compared with the rest of Somalia, but another northern semi-autonomous region - Puntland - has become out-of-bounds for international aid workers since several kidnappings.

Puntland wants to remain part of Somalia. Somaliland declared independence in 1991 and, although not recognised internationally, it has a functioning government, police force and currency.

More than 1.2 million people are displaced inside Somalia, according to the U.N. refugee agency, UNHCR.

Since renewed fighting started in May 2009, more than 200,000 people have been displaced, half of them in June alone, the U.N. Office for the Coordination of Humanitarian Affairs in Somalia (OCHA) says. It is the largest displacement from Mogadishu since the Ethiopian campaign in 2007.

Mogadishu has become so dangerous since Islamists were ousted in 2006 that the majority of its inhabitants have fled, leaving entire neighbourhoods empty.

Many of the uprooted have sought refuge with relatives and friends, often sharing cramped rooms with several other families. Others are in makeshift shelters.

So many people are camped along the 15 km (10 mile) stretch of road west out of Mogadishu towards the town of Afgoye that the United Nations has said it is probably the largest gathering of displaced people in the world, with more than 400,000 people living there in July 2009.

Most of the newly displaced are concentrated in southern and central regions where drought and record high food prices are already making it hard to scrape a living.

Hundreds of thousands of Somali refugees have sought asylum in neighbouring countries, UNHCR says.

Hundreds have drowned making the dangerous sea crossing to Yemen, which they see as a gateway to wealthier parts of the Middle East and the West. Others are crammed into sprawling camps in Dadaab in northeast Kenya, which are regularly hit by flooding and drought. Many have also sought asylum in Ethiopia and Djibouti.

UNHCR says the international community has failed to respond adequately to the plight of Somalia's displaced people, and aid agencies have suffered a severe shortfall in funding.

In the absence of a functioning government, there is no bilateral aid to Somalia.

Some of the country's displacement is caused by persistent drought.

A large proportion of rural Somalis are semi-nomadic, but years of drought have forced many to move their families to towns and villages in search of food and water.

Agencies say many communities - particularly pastoralists - have used up all their emergency supplies and will need support for several years to recover.

In November 2006, just as the country was emerging from the grip of its worst drought in a decade, it was hit by floods that were described as the worst in 50 years.

They washed away homes, roads and bridges in south and central Somalia, affecting some 300,000 people.

Public infrastructure has crumbled, leaving most parts of the country without basic services and contributing to some of the highest maternal and infant mortality rates in the world.

Most child deaths are from diarrhoea, respiratory infections and malaria, according to the U.N. Children's Fund, UNICEF.

Cholera is endemic in Mogadishu due to an absence of basic sanitation or a centralised water supply system, the World Health Organisation (WHO) says.

Malaria - carried by mosquitoes and often fatal - affects an estimated 87 percent of Somalis.

Polio re-emerged in 2005 from a strain that originated in Nigeria, three years after the crippling disease had been wiped out in Somalia. Despite ongoing insecurity, a U.N. vaccination programme was carried out by 10,000 volunteers across the country and in early 2008 WHO said the virus had been eradicated again.

After the Indian Ocean tsunami of December 2004, there were reports of toxic materials being washed up along Somalia's shoreline. Hundreds of people in fishing communities complained of acute respiratory infections, unusual skin conditions, bleeding mouths and sudden death after inhaling toxic materials. Some experts believe the chemicals, including some radioactive material, had been illegally dumped in Somalia's waters.

Somalia has had no functioning government since warlords from rival clans ousted military dictator Mohamed Siad Barre in 1991, failed to agree on a new leader and plunged the country into conflict.

That upheaval - which displaced some 2 million people - coincided with a serious drought. The deadly combination of hunger and displacement pushed almost 4.5 million people - more than half the population - to the brink of starvation by 1992, according to a U.N. report issued five years later. It said 300,000 people, many of them children, died from hunger-related disease during this catastrophe.

In 1992, the United States sent in troops ahead of a U.N. force, but left two years later after tough resistance from warlords, including clashes in 1993 that killed 18 U.S. soldiers and hundreds of Somali militiamen.

Memories of this humiliating incident, which inspired Hollywood movie "Black Hawk Down", have left the international community reluctant to get involved in Somalia again.

The U.N. mission was also unable to end the fighting or safeguard humanitarian aid. It left in 1995.

There have been repeated attempts to restore normal government. In 2004, an interim government-in-exile was formed in Kenya, as Somalia was considered too dangerous a base.

The transitional government was plagued from the start by tensions between rival warlords and its arrival in Somalia was delayed by disagreements on where to house the government and whether to accept foreign peacekeepers.

A faction led by parliamentary speaker Sharif Hassan Sheikh Adan decided to base itself in Mogadishu, while President Abdullahi Yusuf said it was too dangerous, and moved his faction to the provincial city of Jowhar, 90 km (55 miles) north of the capital.

The government has been virtually powerless, depending on foreign backing and warlord alliances for its survival.

The first prime minister of the interim government, Mohammed Ali Gedi, resigned in late 2007, deeply unpopular for his refusal to negotiate with Islamists. He was succeeded by Nur Hassan Hussein.

Yusuf resigned in December 2008 after becoming increasingly isolated both nationally and internationally. He was blamed for hindering a U.N.-hosted peace process and lost parliamentary support over his decision to sack Hussein.

Parliament elected a new moderate Islamist president, Sheikh Sharif Ahmed, in early 2009. Ahmed headed the sharia courts movement that brought some stability to Mogadishu and most of south Somalia in 2006, before Washington's main regional ally Ethiopia invaded to oust them.

His hardline former allies have declared war on his government and called him a traitor.

Ahmed has picked Omar Abdirashid Ali Sharmarke to be prime minister in a power-sharing government intended to end civil conflict. Sharmarke says resettling the displaced and facilitating international aid are his main priority.

The Union of Islamic Courts (UIC) took control of Mogadishu in 2006, and restored some law and order before being ousted by Ethiopian troops sent in to bolster the weak interim government.

Al Shabaab started out as the youth and military wing of the UIC. Some exiled hardline al Shabaab leaders have been based in Eritrea, which is also keen to oust its old enemy Ethiopia from Somalia. The United States lists al Shabaab as a terrorist organisation and says it has links with al Qaeda.

Between them, the two factions now control much of Somalia while the government retains a tenuous hold over parts of Mogadishu.

When the UIC took control of Mogadishu and a swathe of southern Somalia in June 2006, they fought a coalition of warlords styling themselves as a counterterrorism alliance. By late September, they held all the country's main ports except for those in the northern enclaves of Puntland and Somaliland.

While they signed a pact to recognise Yusuf's government, their formation of a national council, new sharia courts and militia movements were seen as a challenge to the government and soon eclipsed it.

The Islamists sought initially to present a moderate face, saying they wanted to bring order to anarchic Mogadishu. And in many ways, they did. The harbour opened briefly and many of the city's residents said they felt safe for the first time in years.

But many Somalis - although Muslims - disliked the Islamic Courts' extreme stances, which included public executions, restrictions on women's ability to work, a ban on watching soccer's World Cup finals and crackdowns on "un-Islamic" hairstyles.

And the rise of Sheikh Hassan Dahir Aweys - a hardline Muslim cleric on U.N. and U.S. "terrorist" lists - fuelled fears the Islamists wanted a rule resembling that of Afghanistan's Taliban.

Washington made clear it believed the Islamists were linked to al Qaeda, and accused them of sheltering the suspects behind 1998 bomb attacks on U.S. embassies in Nairobi and Dar es Salaam.

Ethiopia, a U.S. ally, deployed its troops across the border in 2006 to defend the interim government, and by the end of the year admitted its soldiers were fighting the Islamists.

The United Nations said Eritrea - Ethiopia's arch-enemy - had sent arms to the Islamists, while the Islamists said U.S. money was pouring into Mogadishu to support their enemies.

The perception, justified or otherwise, that U.S. money funded Mogadishu's warlords turned the fighting into a proxy war between Islamist militants and Washington, which was laced with commercial and political motives.

Somali government forces and their Ethiopian allies took back Mogadishu at the end of 2006, and seized the last remaining Islamist stronghold in the south on New Year's Day 2007.

But the Islamists have regained large swathes of territory and, by July 2009, they controlled much of southern and central Somalia, and parts of the capital.

At least 18,000 people have been killed in the violence since the beginning of 2007.

Having failed to end the insurgency, Ethiopia withdrew its troops in early 2009.

Among the Islamist groups is Hizbul Islam, an umbrella organisation of four opposition groups led by hardline cleric Sheikh Hassan Dahir Aweys. The group is aligned and fights alongside al Shabaab in a bid to topple the Western-backed government, which has received weapons from Washington in 2009.

Ahlu Sunna Waljamaca is a moderate Islamist group aligned with the government. The group is led by Sufi clerics and has fought and successfully beaten back al Shabaab in parts of central Somalia. Stung by some al Shabaab practices including desecration of graves, it has vowed to oust the group from other areas. It says the Somali war is sponsored by al Qaeda and other forces, and has nothing to do with Islam.

Many analysts say that U.S. fears of al Qaeda involvement were probably initially baseless but became a self-fulfilling prophesy. In January 2007, al Qaeda urged the Islamists to launch an Iraq-style insurgency against the Ethiopian military in Somalia.

A U.S. gunship attack on a village in southern Somalia in early 2007 - the first known direct U.S. military intervention in Somalia since its failed peacekeeping mission in 1994 - turned into a PR fiasco when it turned out that the 20 or more people killed were civilians, and not fugitive al Qaeda suspects.

Rights groups say various sides, including the Ethiopians, have used excessive force with little regard for civilian casualties.

About 6,500 people were killed in 2007 in Mogadishu alone.

AU peacekeepers have been unable to stem the Islamist insurgency and have found themselves under attack. They complain of being under-funded and under-staffed. However, they have succeeded in reviving Mogadishu's port, turning it into a thriving business centre.

While the 15 U.N. Security Council members agree the situation is dire, many are reluctant to send U.N. peacekeepers, and most observers say a U.N. peacekeeping mission is unlikely while there is no peace to keep.

Despite a U.N. arms embargo, arms shipments to Somali militants have not stopped.

The African Union wants the Security Council to slap sanctions on Eritrea for breaking the embargo, and impose a blockade of Somalia's sea and air ports.

The Security Council has received reports that "elements" of the AU peacekeeping mission and the transitional government are involved in arms trafficking, and most ammunition available in Somali arms markets has been supplied by government and Ethiopian troops.

Most political decisions in Somalia are related to clan loyalties.

The country's four major clans - the Dir, Isaaq, Hawiye and the Darod - are collectively known as Samaale. They are primarily nomadic and live in Somalia, Ethiopia, Kenya and Djibouti.

The original Somali nation was divided up between British, French, Italian and Ethiopian colonies, which accounts for the spill-over of Samaale into neighbouring countries today.

Two other clans, the Digil and the Raxanweyn, are known as Sab. Most Sab live in villages in southern Somalia where they farm and keep livestock.

The most powerfully armed clan is the Hawiye group, whose sub-clans have a long history of conflict that has defied all attempts at pacification.

Though competition between Somalia's clans is nothing new, former dictator Siad Barre - a Darod who ruled Somalia for over 20 years - fuelled conflict by manipulating clan and sub-clan loyalties.

When he was ousted in 1991, the scene was already set for widespread violence. The group that helped topple him - the United Somali Congress (USC), drawn from the Hawiye clan - then split over who should rule.

A wealthy businessman, Ali Mahdi Mohammed, backed by the Hawiye's Abgal sub-clan, nominated himself as president. But General Mohammed Farah Aideed, the USC's main military commander backed by another sub-clan, the Habr Gedir, wanted power for himself.

Former President Abdullahi Yusuf, who quit in 2008, was a Darod. He backed the U.S.-led "war on terror" and was no friend to radical Islamic groups within Somalia. After the Islamists' ouster from Mogadishu, one of the main challenges facing Yusuf and the interim government was to make peace with the Hawiye clan based in the capital.

Analysts say a lasting political settlement is unlikely unless the government agrees to share power in a way acceptable to the main clans.

Somalia's new president is a Hawiye, but has chosen as prime minister a Western-educated Darod to try to broaden the appeal of his government at home and abroad.