The incidents underscored increasing violence in the predominantly Kurdish southeast, where the rebel Kurdistan Workers' Party (PKK) has been waging a bloody separatist campaign.

Two assailants, believed to be PKK members, opened cross-fire with rifles on a police van while it was driving through the center of the city of Batman, the sources said, adding that a security operation was under way to hunt them down.

Two of the six wounded policemen sustained serious injuries, Anatolia news agency reported.

In a separate incident earlier Monday, a passer-by was injured when a time bomb exploded under the car of an army officer, parked outside his home in the town of Idil, near the borders with Iraq and Syria.

The authorities suspect the blast was the work of the PKK, which has often carried out similar attacks in the past.

At the weekend, a radical Kurdish group which the authorities say is a cover-up for the PKK, claimed responsibility for a bomb attack targeting a police building in the western city of Izmir, which left one person injured.

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

Unrest in the region has significantly escalated since June 2004 when the PKK called off a five-year unilateral ceasefire with the government.