The clash took place late Wednesday in the countryside of Mardin province, on the border with Syria, they said.

A large-scale security operation is also under way in the neighbouring province of Sirnak, where 12 people travelling on a minibus were killed last weekend in an ambush blamed on the PKK.

The victims of the attack, the deadliest attributed to the PKK in recent years, were construction workers and village guards, government-armed Kurdish militias supporting the army against the rebels.

The PKK, listed as a terrorist group by Turkey and much of the international community, has waged a bloody campaign for self-rule in Turkey's mainly Kurdish east and southeast since 1984. The conflict has claimed more than 37,000 lives.

Last week, Turkey and Iraq signed an agreement aimed at combatting the PKK, whose militants take refuge in neighbouring northern Iraq and use bases in the region to mount attacks on Turkish targets across the border.