The casualties were on a team of village guards -- local Kurdish men supporting the army against the militants -- assisting a security operation near the town of Semdinli against the outlawed Kurdistan Workers' Party (PKK), the source, speaking on condition of anonymity, said.

The PKK -- considered a terrorist group by Turkey, the United States and the European Union -- has been fighting for a separate state in the mainly Kurdish southeast and east of Turkey since 1984.

The conflict has left more than 37,000 dead.

Turkey alleges that thousands of PKK militants are holed up in rear bases in northern Iraq and has carried out several cross-border air strikes and a week-long ground incursion against rebels bases since December.