Soldiers were scouring the rugged Kupeli and Gabar mountains in Sirnak province for Kurdistan Workers' Party (PKK) rebels under air cover from Cobra attack helicopters and support from Sikorsky troop carriers, said the sources on condition of anonymity.

The general staff said on Wednesday that troops killed 11 PKK rebels and captured two others in the mountains of Sirnak since Tuesday.

There were no reports of a fresh cross-border operation after Turkish warplanes bombed PKK targets in northern Iraq on Wednesday, the third such bombing raid that the army has confirmed since December 16.

Turkey has massed up to 100,000 soldiers in its southeast near the Iraqi border, and in October the Ankara government secured a one-year parliamentary authorisation for cross-border military action to hunt down PKK rebels.

The PKK has been fighting for self-rule in Turkey's mainly Kurdish southeast since 1984, in a conflict that has claimed more than 37,000 lives.

The group is listed as a terrorist organisation by Turkey, the United States and the European Union.