The deputy chairman of the pro-Kurdish Peoples' Democratic Party (HDP), Alp Altinors, has been arrested during a raid by Turkish police, the party said Friday.
Altinors' house in Ankara was searched during the night, the HDP said.
"We protest and condemn this clear act of aggression as a further example of the campaign of repression against the HDP and the forces of the democratic opposition," the HDP said.
Turkish President Recep Tayyip Erdogan accuses the HDP, the second largest opposition party, of supporting the banned Kurdistan Workers' Party (PKK).
The leader of the HDP's parliamentary party, Idris Baluken, told dpa the reason for Altinors' arrest was a speech he gave after an attack in Ankara in October in which 100 people were killed.
Baluken said he did not know what the content of the speech was.
The public prosecutor has accused the HDP of providing propaganda for the PKK in speeches.
"Every time an HDP member of parliament is arrested or imprisoned, the reason stated is a speech that they once gave," Baluken said.