A U.S.-based Muslim cleric, who has become Turkish President Recep Tayyip Erdogan's chief foe, is being tried in absentia, accused of attempting to overthrow the government by masterminding corruption probes in 2013 that targeted people close to the Turkish leader.

The trial of Fethullah Gulen and 68 other people, including former police chiefs, opened in Istanbul on Wednesday.

The government alleges that the corruption allegations against government ministers and Erdogan's son were part of plot by Gulen's movement to bring down Erdogan's government. Gulen, who is living in self-exile in Pennsylvania, has denied the accusations.

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.