The sources said fighters from the Kurdistan Workers Party (PKK) attacked a vehicle carrying paramilitary forces to a post in Kigi, Bingol province late Tuesday.

An operation was launched to find the attackers, the sources said.

The PKK, considered a terrorist group by Turkey, the United States and the European Union, has been fighting for a separate state in southeast Turkey since 1984. The conflict has left more than 37,000 dead.

The Turkish army has stepped up its campaign against the PKK since December, even carrying out cross border air and land attacks on PKK camps in northern Iraq.

Turkey has blamed the PKK for a series of attacks, including a July 27 bomb blasts in Istanbul which left 17 dead and more than 150 wounded.