A U.S.-based Muslim cleric, Fethullah Gulen, who has become Turkish President Recep Tayyip Erdogan's chief foe went on trial in absentia in Istanbul on Wednesday, accused of attempting to overthrow the government by instigating corruption probes in 2013 that targeted people close to the Turkish leader.

Gulen lives in self-imposed exile in Pennsylvania. His passport was revoked in February 2015. He and 68 other people, including former police chiefs, have been charged with "attempting to overthrow the Turkish republic through the use of violence," leading a terrorist organization and "political espionage." Prosecutors are seeking life imprisonment for him and others. He has denied the accusations.

In the opening hearing, Muammer Aydin, a lawyer representing Gulen, asked for the court to dismiss the case, arguing it should not be trying a case concerning crimes against the state, the state-run Anadolu Agency reported. "The accusation against the defendants is attempted coup," it quoted him as saying. "Coups are conducted against the state. The government is in Ankara. The place for trial is Ankara."

The government has been cracking down on Gulen's moderate Islamic movement since December 2013, when prosecutors launched a corruption investigation implicating four government ministers and other people close to Erdogan, including his son.

Erdogan, who survived the corruption allegations, maintains that the graft probes were part of an attempted coup by the cleric and his followers — who were once allied with Erdogan's ruling Islamic-rooted party.

The Turkish government now claims that Gulen has been running a parallel state by getting his followers into key positions in state institutions, including the police and judiciary. It has labeled the Gulen movement a terrorist organization, although followers are not believed to have been involved in any violent acts.

The trial, in which Erdogan and his son have been named as plaintiffs, is widely seen as part of the clampdown on the movement.

Hundreds of police and judiciary officials suspected of ties to Gulen, including those who initiated the corruption investigations, have been dismissed. Followers, including journalists and academics, have been detained. Last year Turkish authorities seized a bank associated with the movement and took over the management of a media and business group linked to Gulen.

Last month, a lawyer hired by Turkey filed a lawsuit against Gulen in the United States, alleging that he orchestrated human rights abuses against three men in Turkey from his U.S. residence.

Wire services