By Daren Butler
ISTANBUL (Reuters) - Turkish police launched an operation on Friday to detain dozens of people including businessmen perceived to be 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 suspected members of Gulen's network in the police, judiciary, media and a bank founded by his followers.
Erdogan accuses Gulen of trying to unseat him, something the cleric denies.
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 provincial police chief were among those detained.
"I am detained. Probably because we spoke and told the truth. It's not a problem," said a message on a widely followed Twitter account bearing the name and picture of Ercan Tastekin, former police chief in the eastern province of Bingol.
The operation, whose targets included members of the Aktif business association, was part of an investigation into what prosecutors describe as the "Fethullahist terror group", Dogan said. It was not clear what the detainees were accused of.
Police declined to comment on the operation, which comes just over two weeks ahead of a June 7 parliamentary election which Erdogan hopes will pave the way for constitutional reform boosting his presidential powers.
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.
Erdogan's opponents say the crackdown on dissent is not limited to members of Gulen's Hizmet (Service) network.
Erdogan has also stepped up criticism of leading media group Dogan and in a television interview late on Thursday lambasted its writers as "charlatans with salaries", holding up examples of Hurriyet newspaper front pages attacking him.
A prosecutor has filed a criminal compliant against Hurriyet editors over a headline he said suggested Erdogan could share the same fate as ousted Egyptian president Mohamed Mursi, for whom an Egyptian court has sought the death penalty.
Hurriyet has rejected the allegations.
(Additional reporting by Humeyra Pamuk; Editing by Nick Tattersall and Robin Pomeroy)