Turkish authorities on Friday widened their post-coup crackdown to the business sector, detaining three top tycoons as part of investigations into the activities of US-based preacher Fethullah Gulen.

Turkish authorities on Friday widened their post-coup crackdown to the business sector, detaining three top tycoons as part of investigations into the activities of US-based preacher Fethullah Gulen.

Security forces in the central city of Kayseri detained the chairman of the family-owned Boydak Holding company, Mustafa Boydak, and two other top executives, state-run Anadolu news agency said.

He and the two other executives -- Sukru and Halit Boydak -- were detained at their homes. Efforts were continuing to detain former chairman Haci Boydak as well as Ilyas and Bekir Boydak for whom warrants have also been issued.

The detentions were part of an investigation into the financing of Gulen's activities in Turkey. Ankara blames the reclusive cleric for the failed July 15 coup aimed at unseating President Recep Tayyip Erdogan.

These appear to be the first major arrests targeting the business world in a crackdown that has already sought to eradicate Gulen's influence from the military, legal system, education and civil service.

Mustafa Boydak is also the head of the chamber of commerce in Kayseri, a fast growing city dubbed one of the "Anatolian Tigers" for the growth and prosperity it has enjoyed under Erdogan's rule.

Boydak Holding has interests in furniture, energy and finance, and notably owns the prominent Istikbal and Bellona furniture firms.

Family-owned holding companies form the backbone of the corporate economy in Turkey, owning many of its most famous brands.

Almost 16,000 people have been detained so far in the nationwide crackdown, the magnitude of which has caused international alarm.