A memorandum issued after the February 28, 1997 meeting of Turkey's top military leadership precipitated the fall of the government led by prime minister Necmettin Erbakan, the mentor of current President Recep Tayyip Erdogan.

The move by the army's leadership to undermine Erbakan's government did not extend to fully-fledged military action and it is often called the "post-modern coup".

An Ankara court sentenced the 21 accused, including former general staff chief Ismail Hakki Karadayi, former top general Cevik Bir and ex army commander Cetin Dogan, to life in prison over their roles, the state-run Anadolu news agency said.

Another 68 suspects were acquitted. The CNN-Turk channel said those convicted would be spared going to jail on age grounds but this was not immediately confirmed.

A total of 103 suspects had initially been put on trial in September 2013 but several died in the course of the long legal process.

Erbakan led the Welfare Party and was the first Islamic-rooted leader in the modern history of officially secular Turkey.

It was out of Welfare that Erdogan and several comrades founded the Islamic-rooted Justice and Development Party (AKP) which has ruled Turkey since 2002.

The army, which sees itself as the guarantor of Turkey's secular principles, had overthrown three earlier administrations in 1960, 1971 and 1980.

Rogue elements within the army sought to topple Erdogan on July 15, 2016 in a coup bid the government blames on the US-based preacher Fethullah Gulen. Gulen denies the charges.