By Ibon Villelabeitia

ANKARA, Jan 16 (Reuters) - Turkey's powerful military on Friday criticised a widening investigation into an alleged coup plot that has led to the arrests of several senior officers.

Eighty-six people including retired army officers, politicians and lawyers are on trial in a case that has rattled markets and raised tensions between the Islamist-rooted AK Party government and the secularist establishment in the EU candidate.

In the military's first comments since police arrested last week more than 40 people including senior ranking officers, the General Staff said the probe into the right-wing "Ergenekon" group was damaging the Turkish state.

"Basic human rights and principles of law are being breached, like the constitutional principle of nobody is guilty unless found so by a court, or the principle of innocence and right to a fair trial," Brigadier General Metin Gurak, spokesman for the General Staff, told a news conference.

"Those who are expected to act responsibly are hurting individuals, institutions, the judiciary and finally the state itself," Gurak said.

The detention of officers has caused deep concern in Turkey's powerful military, which has enjoyed an untouchable status since the foundation of modern Turkey and which has unseated governments four times in the past 50 years.

The widening investigation has rattled Turkish markets, already hurt by the global financial crisis. Analysts have warned the probe may be explosive in a country with a long history of political instability and threatens to complicate Ankara's efforts to tackle economic turmoil.

PRESIDENT URGES RESTRAINT

President Abdullah Gul on Friday urged Turkish media, which have gone into a frenzy over the Ergenekon probe with 24-hour coverage, to act responsibly.

"Nobody should exert pressure on the judiciary in this process and the media should refrain from puttting forward names of many people in the media in an irresponsible way," he told a news conference.

The secularist establishment, which includes the army generals, judges and the state bureaucracy, views the arrests as a revenge by the governing AK Party for a 2008 court case that sought to ban the party for anti-secular activities.

The AK Party, which embraces centre-right elements and nationalists as well as religious conservatives, denies this.

While analysts agree that the coup investigation has unearthed serious criminal activities, some say the increasingly far-fetched links between Ergenekon and unresolved murders over the past decades undermines the credibility of the case.

Turkey's leading opposition Republican People's Party (CHP) has criticised state television broadcaster TRT for airing a live interview with a prime Ergenekon informant in exile in Canada where he accused hundreds of people, including the CHP leader, top generals, journalists and businessmen of being members of Ergenekon or the Turkish intelligence services.

Prosecutors accuse the shadowy "Ergenekon" group of plotting to engineer an army coup by launching a campaign of bombings and assassinations. The suspected members of the group are also accused of numerous assassinations over the past few years. (Editing by Richard Balmforth)

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