Nominal life sentences for the three former generals on Friday were the first penalties to be handed down in the trial of hundreds of officers, which has lasted for two years.

But the court sitting at Siliviri, near Istanbul, said that the three would only serve 20-year prison sentences, since they had been unsuccessful in their coup attempt.

A further 323 defendants, who had claimed they were innocent of the charges, were sentenced to up to 18 years in prison. The three chief suspects included Cetin Dogan, a former army commander who was dubbed the "mastermind" behind the alleged 2003 plot.

Those implicated were accused of conspiring to overthrow the Islamic-leaning government of Prime Minister Recep Tayyip Erdogan.

Turkey's military has long played a major role in politics, having staged three coups between 1960 and 1980. It came to be seen as the guardian of the country's secular political system, founded by Mustafa Kemal Ataturk, and pressured the country's first Islamic-led government out of office in 1997.

Dogan slammed the trial as "unfair and unlawful" on Thursday, according to a transcript of his testimony.

"Here we see a process unfolding to make the soldiers of Mustafa Kemal, who give their lives for their country, pay for the price of their commitment to the republic and its principles."

Prosecutors alleged that some 364 officers were involved in a secularist plot to pave the way for a military takeover. There were acquittals for 34 of the accused.

Critics claimed the case is aimed at silencing government opponents. The government has said the trial is a landmark move towards greater democracy.

The trial, dubbed "Sledgehammer" after a military exercise in 2005, is the first of its kind to be held in a civilian court. Of those suspected, a total of 250 have been in custody since being arrested.

Military influence has been curtailed somewhat since Erdogan's government came to power.

rc/dr (AP, AFP, Reuters)