An Ankara court has released from jail 10 suspects, including high-ranking officers, pending the outcome of their trial for their alleged role in the 1997 bloodless coup that toppled the Islamist government.

The court on Wednesday released former four-star general Teoman Koman from custody due to ill health. Eight other former officers and a civilian suspect were released on Thursday for medical reasons or on the grounds they did not pose a flight risk.

The suspects had been in custody since 2012, and although the court did not set bail the court ordered them not to leave the country.

A further 27 retired officers on trial in the same case remain in jail.

A total 103 people, including ex-army chief General Ismail Hakki Karadayi, stand accused of overthrowing the government in the trial that began Monday.

Prosecutors have spent the last week reading out the charges.

They have called for a life sentence for Karadayi, 81, who did not attend the hearings due to ill health.

The trial, expected to last several weeks, concerns the toppling in 1997 of Turkey's first Islamist prime minister, Necmettin Erbakan, the political mentor of current Prime Minister Recep Tayyip Erdogan.

The army brought down Erbakan's government without violence and did not install a military administration to replace the civilian cabinet. It became known as the "postmodern coup" as no troops were involved.

Karadayi has denied that the army's actions were tantamount to a coup.

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

Since coming to power in 2002, Erdogan's Islamic-rooted Justice and Development Party (AKP) government has reined in the once-powerful military through a series of court cases.