The fighting erupted when troops patroling a mountainous area in Mardin province came upon militants from the separatist Kurdistan Workers' Party (PKK), the sources said.

A security operation was under way to hunt down the militants.

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

Ankara has vowed to pursue military action against the PKK, while pledging reforms to expand the freedoms of the Kurdish community.