BELGRADE, Yugoslavia - Asserting that outgunned Serbian policemen were besieged Wednesday by ethnic Albanian militants just outside Kosovo, the Yugoslav leadership warned of possible ''large-scale war'' unless urgent international action curbed the alleged offensive.
Over the past two days, at least four Serb policemen have been killed and 10 others wounded in a demilitarized zone in the unofficial border region between Kosovo and central Serbia, said Zoran Djindjic, a key aide to President Vojislav Kostunica.
''This is very dangerous, not only for the situation in Serbia, but also the whole region,'' he warned.
In Kosovo, one Serb was killed and another injured when a large explosion rocked a building used as a residence and offices of the Yugoslav representative early Wednesday.
Though separate, the violence in and outside Kosovo appeared to be linked to ethnic Albanian aspirations for independence from Serbia, the larger of the two Yugoslav republics.
Kostunica's Cabinet met Wednesday to review what the government called the ''latest escalation of terrorist acts by Kosovo Albanian extremists.'' The cabinet dispatched a note to the U.N. Security Council, demanding an urgent session to condemn the attacks and take measures to halt them.
''After expelling 300,000 Serbs and others from Kosovo ... Albanian extremists are now ... blocking international and Yugoslav efforts to find a democratic and civilized solution to the Kosovo crisis,'' read the government statement, warning of the threat of a new regional conflict.
The Security Council responded by adopting a consensus statement Wednesday evening strongly condemning the ''criminal attacks'' and calling for an immediate investigation to bring the perpetrators to justice.
In an unusually rapid response, the 15 ambassadors demanded that all sides refrain from further attacks, particularly against minorities, and called on NATO and the United Nations to take steps to prevent further violence.
Run by the United Nations and NATO under terms of a peace agreement that led to a pullout of forces loyal to Slobodan Milosevic in exchange for an end to NATO bombing last year, Kosovo formally remains part of Serbia.
In the predominately ethnic Albanian Presevo Valley of southern Serbia, dozens have been killed in ethnic Albanian attacks on Serb police. The group, which calls itself the Liberation Army of Presevo, Bujanovac and Medvedja, is fighting for union with Kosovo, which also wants independence.
The new Yugoslav authorities claim that most of the group's attacks are launched from Kosovo and demand better security along the boundary by the more than 35,000 international troops based in Kosovo.
British Flight Lt. Mark A. Whity of NATO said his monitors had recorded around 30 mortar rounds and simultaneous small-arms fire over a four-hour period Tuesday. He had no details of fighting Wednesday.
In Belgrade, Djindjic spoke of ''big clashes,'' saying about 400 ethnic Albanian ''commandoes,'' armed with mortars and other heavy weapons, surrounded a few dozen Serb policemen.
The peace deal, which ended last year's NATO bombing of Yugoslavia, established a 3-mile demilitarized zone along the Kosovo border with central Serbia. Only lightly armed regular Serb police are allowed in.
Djindjic demanded that anti-terrorist Serb police be now let into the demilitarized zone to push the rebels out and suggested Yugoslavia would do so if attacks continue.
One Serb policeman was killed in the clashes overnight, while three more first disappeared and were later reported dead, Djindjic said.