ISTANBUL (Reuters) - Turkey has formally arrested an executive of Dogan Holding, a conglomerate with major media interests, in a widening probe into a U.S.-based cleric Ankara accuses of masterminding July’s attempted coup.

State-run Anadolu agency said late on Thursday that a court had remanded the executive in custody on an accusation of “aiding a terror group” as part of an investigation into the exiled Muslim cleric Fethullah Gulen and his followers.

Ankara refers to the group as the “Gulenist Terror Organisation”.

Dogan Holding, which includes the country’s largest media group, said on Dec. 1 that executive Barbaros Muratoglu was being investigated, triggering concern that a post-coup crackdown may spread to the country’s top companies.

Dogan’s Hurriyet newspaper also reported his formal arrest on its website. Officials from the group were not immediately available to comment.

Since the failed putsch on July 15, authorities have detained or dismissed more than 100,000 people in the police, judiciary and civil service and formally arrested nearly 41,000.

Nearly 600 companies have been also seized, many of them smaller provincial firms, over links to Gulen. The cleric, a former ally turned political foe of President Tayyip Erdogan, has denied involvement in the coup.

Dogan has interests in media, finance, energy and tourism.