The clashes began Thursday when fighters of the Kurdistan Workers Party (PKK) tried to cross into Turkey's Sirnak province near Uludere from bases in Iraq, security sources said.

A second attempt was made on Friday night, the sources said, adding that 12 rebels in total had been killed, four surrendered and numerous weapons seized.

Anatolia news agency reported that the Turkish military had employed combat helicopters.

In a separate incident the agency quoted Hakkari provincial governor Muammer as saying that a Turkish soldier was killed in a mine explosion during a search operation in the mountains.

Reinforcements had been sent to the area with air support, he added.

The PKK, listed as a terrorist group by Turkey and much of the international community, took up arms in 1984, sparking a conflict that has claimed some 45,000 lives.

It declared a ceasefire in August 2010 but clashes with the army have increased in the run-up to Turkish elections scheduled for June 12.