Updated

An explosion rocked a U.N. building in northern Kosovo, causing slight damage but no injuries, just hours after ethnic Albanian leaders in Pristina proclaimed Kosovo's independence.

The blast — apparently caused by a hurled hand grenade — damaged a concrete wall of the building housing a courthouse and jail. Another unexploded hand grenade was discovered across the street near a motel that houses European Union officials, said Besim Hoti, spokesman for Kosovo police.

Kosovska Mitrovica, a city of 60,000 in Kosovo's north divided between Serbs and ethnic Albanians, was tense Sunday after ethnic Albanian leaders in Pristina declared Kosovo's independence.

Helicopters buzzed overhead and police officers patrolled the streets to prevent violence in one of the few areas of Kosovo populated by minority Serbs, who make less than 10 percent of Kosovo's 2 million people.

All of Kosovo has been run by the United Nations, backed by 16,000 NATO troops, since 1999, when NATO launched a bombing campaign to halt a Serb crackdown on ethnic Albanian separatists.

In the coming months, an 1,800-member European Union mission will move in to replace the U.N. and to help build Kosovo's police force and legal system.

The Serbian government in Belgrade has assured Kosovo's defiant Serbs that they will remain Serbian.

Serbia's red, blue and white flag fluttered in the north of Kosovska Mitrovica, which is dominated by Serbs, while ethnic Albanians across the Ibar River in the south launched fireworks and fired guns to celebrate.

"The Albanians can celebrate all they want but this stillborn baby of theirs will never be an independent country as long as we Serbs are here and alive," said Djordje Jovanovic as Serbs chanting "This is Serbia" gathered near the bridge separating them from ethnic Albanians.

Serbia's government minister for Kosovo, Slobodan Samardzic, said Serbia will increase its control over the 15 percent of the province that is inhabited by the Serbs — an apparent attempt to partition Kosovo.

"It's a historic day for the Albanians, but not for us," said Milan Jankovic, sitting in a restaurant sipping plum brandy as Serbian folk music drowned out TV coverage of the declaration.

"Maybe this is good for everyone. At least we'll split for good. We belong to Serbia, and they belong to Albania," Jankovic said.

Ethnic Albanians, who are mostly Muslim, saw Sunday's declaration as a final victory over Serbs in their decades-long struggle over the impoverished territory.

Kosovo's minority Serbs, mostly Christian Orthodox, vowed to defend the province they consider the heart of their medieval statehood and religion.

The Serb attachment to Kosovo dates to 1389, when the province, then the seat of a Serbian state, fell to the Ottoman Turks.

"Another Kosovo battle awaits the Serbian people, this time without swords but with candles, songs and prayers," Milomir Vlaskovic, a priest, said at a Serbian Orthodox church.

Ahmet Jashari, 55, whose shabby house is surrounded by garbage and decorated with the red Albanian flag, said he had been waiting for this "historic" day all his life.

"Serbs have oppressed us, taken our homes, killed our people and downgraded us for decades," Jashari said. "Now this has formally come to an end. We finally have our country."