Two Serbian police officers have been killed by an anti-tank mine in a mainly ethnic Albanian area close to the province of Kosovo.

The police blamed the incident on what they called Albanian terrorist gangs from Kosovo and said a search was under way.

Nine other officers were injured when one of two police vehicles hit the mine near the town of Bujanovac in southern Serbia's Presevo Valley on Friday morning.

The area is not part of United Nations-controlled Kosovo, but nevertheless has a large Albanian population.

Correspondents say a rebel ethnic Albanian group - the Liberation Army of Presevo, Medvedja and Bujanovic - has been fighting the Serb authorities since Nato-led peacekeepers arrived in Kosovo, and Serb forces withdrew last year.

The blast occurred between the villages of Mali and Veliki Trnovac - the latter is an ethnic Albanian community of around 10,000 people.

The blast occured on the edge of the Ground Security Zone, a 5km (three mile) demiliatrised zone set up in terms of an accord between Nato forces and the Yugoslav military after Nato bombed Kosovo last year.

The agreement says only local Serb police may enter the zone.

The Presevo Valley is home to an Albanian militia called the Liberation Army for Presevo, Medvedja and Bujanovac (UCPMB).

About 50 clashes between the UCPMB and the Serbian police have been reported in the past year.