A court ordered the arrest of Sener Eruygur, once head of the paramilitary gendarmerie, and Hursit Tolon, the former first army commander. They were sent to a prison in Istanbul.

Mr Eruygur is head of the Kemalist Thought Association, which helped organise mass anti-government demonstrations last year.

They were among 21 people detained last Tuesday in a police investigation into allegations of a coup. Eight of the detained, including a prominent businessman, had already been arrested.

Media reports said a secret plan was seized during the swoop which called for illegal protests on 7 July across 40 provinces, assassinations and attacks on security forces. They said the two former generals were suspected of being members of a shadowy, ultra-nationalist secularist group known as Ergenekon, which was already under investigation.

Turkey, which is predominantly Muslim but officially secular, and is seeking to join the European Union, has had four military coups against elected government in the past 50 years. No top generals have been arrested for political reasons during that time.

Mr Eruygur's lawyer, Filiz Esen, dismissed the charges as false, saying: We accept none of these accusations."