Dozens of bullets were fired at the van, which was on patrol in the centre of Kiziltepe town, at the Syrian border, witnesses said.

One of the policemen was in serious condition, said an official from the governor's office in Mardin province, where the town is located.

Militants of the separatist Kurdistan Workers' Party (PKK) are believed to be behind the attack, the official said, adding that the security forces surrounded the area in order to hunt down the perpetrators.

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.

Winter lulls in violence are usually broken with the arrival of spring when the snow melts, allowing the rebels to move out from their mountainous hideouts in southeast Turkey and neighbouring Iraq.