PRISTINA, Yugoslavia (AP) - Gunmen fired on a joint American-Russian patrol Sunday as it tried to seal the boundary between Kosovo and part of southern Serbia where ethnic Albanian rebels have been challenging Yugoslav forces, the U.S. Army said.
Peacekeepers suffered no casualties in the attack, the first reported against NATO-led troops since ethnic Albanian rebels escalated cross-border raids in November. The joint patrol returned fire but it was unclear whether the attackers, whose identity was unknown, suffered casualties, U.S. Army spokeswoman Capt. Alayne Cramer said in a statement.
The attack occurred one day after a violent incident in northwestern Kosovo, in which Serbs angry over the arrest of a motorist set fire to a police station, stoned vehicles and briefly took seven Belgian soldiers hostage. Two Serbs died in the melee in the town of Leposavic and one was wounded, raising tensions in this troubled province.
The U.S. statement said the shooting attack occurred about 1:30 p.m. as the patrol was trying to seal the boundary near the village of Gornje Karacevo about 30 miles southeast of Pristina.
Peacekeepers had just detonated a series of explosive charges to destroy a section of road believed used by the militants when they received small arms fire, the statement said.
''The Multinational Brigade East was continuing the boundary closure efforts to prevent the flow of supplies and movement of armed ethnic groups across the border,'' the statement added. ''No suspects have been detained.''
The new democratic government of Yugoslav President Vojislav Kostunica has been urging the NATO-led force in Kosovo to crack down on the ethnic Albanian extremists of the Liberation Army of Presevo, Medvedja and Bujanovac, known by its Albanian-language acronym UCPMB.
Last month, the rebels killed four Yugoslav policemen and seized several positions in the three-mile-wide buffer zone along the Yugoslav side of the boundary. The zone was established in June 1999 to prevent Belgrade's forces from threatening the peacekeepers who took over Kosovo after the 78-day NATO bombing of Yugoslavia, launched to force then-President Slobodan Milosevic to halt his crackdown against Kosovo Albanians.
Yugoslav forces cannot use heavy weapons in the zone, and so the ethnic Albanians have been operating in the area with impunity. They are trying to drive Yugoslav forces from the area, which has an ethnic Albanian majority but is not part of Kosovo.
The incident occurred at a time of mounting tension in the province following Saturday's violence in Leposavic, about 40 miles northwest of here in a predominately Serb area.
Trouble there started Saturday when Serb police working for the U.N.-run Kosovo police force arrested Vladimir Tomovic, a Serb, for speeding and possession of unspecified illegal communications equipment, NATO spokesman Maj. Steven Shappell said.
After the arrest, about 200 Serbs gathered outside the police station, located next to the Belgian army barracks, and stoned a car, Shappell said. Protesters seized seven Belgian soldiers but released them later.
Shortly before midnight Saturday, a much larger crowd converged on the police station again, setting it on fire, destroying the station and three vehicles, NATO said.
NATO said Belgian soldiers fired tear gas and shots into the air, but two demonstrators were wounded.
One later died of his wounds - NATO said the other's life was not in danger - and a 42-year-old protester died of a heart attack. Shappell said an investigation was launched to determine who shot the protesters.
Kostunica traded accusations with Milosevic allies over the Leposavic violence, which occurred a week before parliamentary elections in Yugoslav's main republic Serbia.
In a statement, Kostunica blamed ''those who do not want a peaceful solution to Kosovo's problems'' for stirring up trouble, adding that ''it's no coincidence that this is happening just before Serbia's elections.''
He urged all Serbs, ethnic Albanians as well as international authorities not to ''fall into the trap of those who do not want peace.''
Milosevic's Socialist party and its allies, however, accused Kostunica of failing to defend Serb interests. The Serbian Radical Party said the deaths in Leposavic ''are an example of the fate that awaits all Serbs'' under Kostunica's government.
A local branch of Milosevic's Socialists demanded from Kostunica's government to ''put an end to the crimes against Serbs.''
More than 40 U.N. policemen were evacuated Sunday from the Serb-populated town, located 40 miles northwest of Pristina following the violence, according to U.N. police spokesman Dmitry Kaportsev.
The Belgian peacekeepers remained in their barracks and French troops were sent to reinforce them.
Kaportsev first said ''KFOR shot the Serbs.'' Later, he said an investigation must determine who fired the fatal shot.
Belgium's defense minister, Andre Flahaut, refused to say who fired the fatal shot pending the results of the U.N. investigation. Flahaut met with the Belgian military general staff for two hours Sunday morning to discuss the situation in Kosovo.