Turkish police launched an operation on Friday to detain some 80 business people in an investigation targeting supporters of U.S.-based Muslim cleric Fethullah Gulen, President Tayyip Erdogan's ally-turned-foe, the Dogan news agency said.

Moves against what Erdogan calls a "parallel structure" within the state had until now focused on Gulen's perceived followers in the police, judiciary, media and a major bank. Erdogan accuses Gulen of trying to unseat him.

The police operation was focused on the central city of Konya but spread across more than 10 provinces, Dogan reported, adding that 20 people including a former police chief were among those detained.

Police declined to comment on the operation, which comes just over two weeks ahead of a June 7 parliamentary election.

Erdogan blames Gulen's supporters within the police and judiciary for instigating a corruption inquiry that rocked the government late in 2013.

Thousands of police officers, judges and prosecutors were subsequently removed from their posts or transferred to other duties, while the court cases they instigated have been dismissed.