Turkish police launched a vast operation on Thursday against businesses suspected of financing US-based Muslim preacher Fethullah Gulen, as an investigation into suspects in last month's failed military rebellion shifted to the private sector.

Prosecutors issued 187 arrest warrants as part of the operation in the country's economic capital of Istanbul and other provinces, CNN-Turk reported.

It said around 1,000 police took part in the operation in 15 provinces, which included simultaneous raids in about 100 addresses in several districts of Istanbul as well as 100 others in other parts of the country.

The suspects are accused of financing the activities of Gulen, blamed by authorities for orchestrating the 15 July putsch attempt.

In a similar operation on Tuesday, Turkish police raided dozens of companies in Istanbul in search of 120 suspects. Around 100 people were detained.

Prime Minister Binali Yildirim said late on Wednesday that 40,029 state employees have been detained in the crackdown on alleged Gulen supporters in the wake of the failed 15 July coup, of whom 20,335 have been remanded in custody.

More than 5,000 civil servants have been dismissed and almost 80,000 others suspended, he said in an interview with TRT public television.

President Recep Tayyip Erdogan has vowed to eradicate businesses, charities and schools linked to Gulen, calling them "terror organisations" and "nests of terror".

Gulen, a reclusive cleric who has lived in the US since 1999, has been repeatedly accused of running a "parallel state" since a corruption scandal embroiling then premier Erdogan and several of his ministers erupted in 2013.

Gulen, in self-imposed exile, has denied the government's accusations.

Ankara wants Washington to extradite Gulen to face trial back home, indicating that any failure to deliver him will severely damage ties.