An ethnic Albanian mob hauled three Serbs from their car, shot one dead and assaulted the others as celebrations marking a key date in Albanian history turned ugly, international officials said today.

The overnight attack took place in central Pristina, capital of the Serbian province of Kosovo, as thousands of people celebrated Flag Day, which recalls both a 15th century Albanian uprising against Ottoman rule and the 1912 declaration of Albanian independence.

The attackers killed a 52-year-old man, assaulted his wife and his 76-year-old mother-in-law and set fire to the victims' car, Kosovo's international police force said.

A crowd of about 2,000 people obstructed police and troops from the NATO-led peacekeeping force as they tried to reach the scene, throwing firecrackers, insulting police trainees and urging them to join the attackers, police said.

"I'm appalled by what happened," said Gen. Klaus Reinhardt, commander of NATO forces in Kosovo. "For me, it unveils a basic lack of humanity by the people in the street and a high degree of intolerance on the side of the attackers and the bystanders."

Kosovo's ethnic Albanian majority had been banned from marking Flag Day under Serbian rule in the province, which effectively ended when NATO bombing drove out Serbian forces earlier this year.