PRISTINA, Kosovo (AP): Hundreds of Serbs stormed a U.N. courthouse in northern Kosovo on Friday, taking control of the site and hoisting a Serbian flag to replace a U.N. one.

They broke through two gates at the front of the three-story building at about 8:30 a.m. (0730 GMT) and pushed aside U.N. riot police guarding the courthouse in the northern Serb-dominated city of Kosovska Mitrovica, a police spokesman said.

Dozens of U.N. police guards based there did not intervene.

By late afternoon the U.N. flag had been raised again, but about 100 of the Serbs remained in the compound or locked inside the courthouse, saying they would not leave until they reached a deal with U.N. officials, Kosovo police said.

``We tried to negotiate, but no one wanted to talk to us,'' said Miodrag Ralic, one of the Serb protest leaders. ``We could not wait any longer.''

``We have nothing against international judges,'' said Nebojsa Jovic, another leader. ``We want to cooperate with all non-Albanians and all those who do not recognize independent Kosovo.''

Some of the Serbs who stormed the building worked in Serbia's justice system before Kosovo came under U.N. and NATO control in 1999, and have refused to work under the U.N. administration. Following Kosovo's declaration of independence, minority Serbs have threatened to set up parallel offices that report directly to Belgrade.

The attack on the courthouse was condemned by the European Union and by NATO Secretary General Jaap de Hoop Scheffer, who made a previously planned visit to Kosovo on Friday.

Serbs have held daily protests in front of the court since Kosovo declared independence from Serbia on Feb. 17.

Kosovo, which is predominantly ethnic Albanian, came under U.N. control when NATO launched an air war to stop Slobodan Milosevic's crackdown on ethnic Albanian separatists. Serbia, which considers the territory its historic and religious heartland, says Kosovo's declaration of independence was illegal under international law.

Joachim Ruecker, the top U.N. official in Kosovo, said Friday that he had ordered the U.N. police to retake the court building, and he pledged to defend his mandate as head of the U.N. mission known as UNMIK.

``Those who turned to violence in North Mitrovica have crossed one of UNMIK's red lines. This is completely unacceptable,'' Ruecker said in a statement. ``I have instructed UNMIK police to restore law and order in the north and to ensure that the courthouse is again under U.N. control.'' He said the attackers would be prosecuted and urged Serbian authorities to prevent further such incidents.