Turkish prosecutors are demanding jail terms of up to 20 years for 365 active and retired soldiers accused of plotting to undermine the Islamist-rooted government, state media reported Thursday.

Among those facing trial in the "Operation Sledgehammer" case are several former generals including alleged plot organiser General Cetin Dogan. They are accused of trying to use force to block the Turkish government.

The plot was allegedly drawn up shortly after the Justice and Development Party came to power in November 2002, amid fears it would undermine Turkey's secular system.

The military, which considers itself the guardian of secularism in modern Turkey and is the second-largest force in NATO after the United States, has carried out three coups -- in 1960, 1971 and 1980.

Prosecutors outlined their case Thursday in a 920-page document.

Of the defendants in the case, 250 are in pretrial custody.

The investigation, the toughest challenge yet to the once-omnipotent military, has landed more than 30 generals, or about a tenth of the total, in jail.

But the case has been marred by serious doubts over the authenticity of some implicating documents, fuelling mistrust between the army and government.

The soldiers allegedly plotted to bomb mosques, and down a Turkish jet over the Aegean and blame it on Greece, hoping to discredit the government and garner public support for a coup.

Dogan, the alleged plot leader, says papers from a seminar on a contingency plan based on a scenario of tensions with Greece and domestic unrest were doctored to look like a coup plan.