The sources referred to the mass raids as a "counter-terror" operation.

State media TRT reported that police held people suspected of financing the outlawed Kurdistan Workers' Party (PKK) or roping in new members to the group.

Deemed a terrorist organisation by the United States, the European Union and Turkey, the PKK has been waging a decades-long armed struggle against Ankara for greater autonomy for the Kurdish minority.

The Diyarbakir bar association said the number of detentions could be as high as 150, adding that they included 20 lawyers, five journalists, three actors and one politician.

The operation comes a few weeks ahead of a crucial vote.

Turkey's main pro-Kurdish party, The Peoples' Democratic Party (HDP), said last month it would not field a presidential candidate in May 14 elections, giving tacit support to President Recep Tayyip Erdogan's secular rival.