The fighting erupted late Tuesday at Kato mountain near Uludere town in Sirnak province, which borders Iraq and Syria, the sources said.

The casualties included two soldiers and three Kurdish militia paid by the government to assist in fighting against rebels of the outlawed Kurdistan Workers" Party (PKK).

The clashes come a day after two soldiers and two PKK rebels were killed in the same area.

Fighting between the army and the rebels have significantly escalated this year and Kurdish militants have claimed a series of bomb attacks in urban centers.

The army has amassed troops in the southeast to step up security operations and stop what it says are increasing rebel incursions from neighboring northern Iraq, where the PKK took refuge after declaring a unilateral ceasefire in 1999. The truce was called off in June 2004.

The Kurdish conflict has claimed more than 37,000 lives since 1984 when the PKK, blacklisted as a terrorist group by Turkey, the European Union and the United States, took up arms for Kurdish self-rule in the southeast.