(Updates with U.S. comment)

By Ivana Sekuralac and Dina Kyriakidou

BELGRADE, June 11 (Reuters) - Serbia arrested a top Bosnian Serb war crimes fugitive on Wednesday and will hand him to the U.N. tribunal in The Hague, earning praise from the European Union and the United States.

Bosnian Serb security chief Stojan Zupljanin, 56, was one of four suspects sought by the tribunal for war crimes in the territory of former Yugoslavia in the 1990s.

Their arrest and handover to the tribunal has been a condition of Serbia's progress towards EU membership.

"There was no resistance during his arrest," said Vladimir Vukcevic, Serbia's chief war crimes prosecutor, who coordinated the operation. "This arrest shows clearly that we are seriously cooperating (with the Hague)."

Zupljanin was found at an apartment about 8 km (5 miles) from the centre of Belgrade by police and security agents and will be extradited within in 72 hours, officials said.

The arrest comes as Serbia, deeply split between nationalists and a pro-EU bloc after inconclusive elections last month, is immersed in intense coalition negotiations.

Officials said Zupljanin had foiled a previous attempt to arrest him in the southern Serbian city of Nis two months ago. His family had publicly called on him to surrender, to spare them further notoriety and financial collapse.

Zupljanin, a commander in the city of Banja Luka during the 1992-95 Bosnian war, is charged with killing Muslim and Croat civilians. The president of the association of former detainees in Banja Luka said the arrest will bring relief to the victims.

"This is a very good news for all people who survived the arrests and tortures in Banja Luka," said Zijahudin Smailagic. "I hope that executors of Zupljanin's orders, who now walk freely in Banja Luka, will also be arrested."

STILL AT LARGE

Also still at large, 13 years after the war ended, are the Bosnian Serb military commander Ratko Mladic, Bosnian Serb political leader Radovan Karadzic and Goran Hadzic, a local Croatian Serb leader.

The U.N.'s chief prosecutor for Yugoslavia war crimes, Serge Brammertz, told the U.N. Security Council last week he believed all four were within Serbia's reach and urged the new government to arrest them.

The EU welcomed the arrest.

"It is an important step towards full cooperation with (the tribunal), which is key to bringing justice and lasting reconciliation in the Western Balkans region," EU Enlargement Commissioner Olli Rehn said in a statement.

In Washington, the State Department also praised Serbia.

"His arrest is another positive step towards insuring those responsible for war crimes committed in the former Yugoslavia are held accountable," said State Department spokesman Gonzalo Gallegos.

The U.S. hoped the arrest of Mladic, Karadzic and Hadzic, would follow, and "we call on authorities in the region to bring them to justice," he said.

Analysts said Wednesday's arrest may indicate that a pro-European coalition was the most likely outcome of Serbia's month-long government negotiations.

"It might also be seen as an announcement that it's more realistic to have a government that will follow a pro-European path," said political analyst Zoran Stojiljkovic.

The Democratic party leading the pro-Western bloc said the arrest signalled Serbia may gain EU candidate status by the end of the year. The Radical party, spearheading the nationalist grouping, slammed it as a black page in Serbia's history.

"The Hague tribunal is an instrument of the U.S. and the West, that serves to put pressure on Serbia and justify all the crimes committed against our nation," Radical party vice-president Dragan Todorovic said.

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