The state-run Anatolian Agency reported operations were launched in five provinces including Istanbul and Ankara, and the western cities of Izmir and Manisa as well as the eastern province of Van.

The operation was launched and conducted by the Gendarmerie Command Headquarters of Izmir, the report said.

Teachers and union officials were among those detained in the operations, it added. The gendarmerie searched the office of an executive of the Confederation of Public Employees Trade Unions, or KESK, in Ankara, according to the agency.

Union officials confirmed that two KESK members were taken into custody and that searches were conducted in the offices as part of the operation, which they defined as "unacceptable".

"This is said to be an anti-terror operation, and they are trying to link KESK to this. It is impossible to accept this," the general secretary of KESK, Emirali Simsek, told reporters in a televised press conference.

He slammed the searches of the KESK office, saying it was a "threat" to the elements of democracy and labor rights. A number of KESK members were present and chanted anti-government slogans during the conference.

Turkish authorities detained dozens of people, including members of the pro-Kurdish Democratic Society Party, or DTP, in a crackdown on suspected PKK supporters earlier in April. It is yet to be confirmed whether Thursday's detentions were related to the earlier operation.

* Photo is an archive image taken during similar operations earlier in April