Authorities in Turkey have issued detention warrants for 249 people as part of an investigation into alleged cheating during exams to recruit staff to the country's foreign ministry between 2010 and 2013.

The Ankara Chief Prosecutor's office says 91 of the suspects were detained on Monday.

The suspects are believed to have links to the network led by U.S.-based Muslim cleric Fethullah Gulen, who is accused of orchestrating a failed coup attempt in 2016. Gulen denies the accusation.

Authorities believe Gulen's network, which has been outlawed, has helped followers infiltrate key civil service jobs through cheating and other means.

Some 77,000 people have been arrested for links to Gulen since the coup and around 130,000 others have been dismissed from state jobs.