Hundreds of protesters storm building in Mitrovica and hoist the Serbian flag.
Beshim Hoti, a spokesman for Kosovo police, said that UN police were targeted as they tried to arrest Serbs inside the courthouse.
A group of about 300 Serb protesters opposed to Kosovo’s independence took control the UN-run courthouse last Friday.
They refused to leave the premises after negotiations with UN officials failed over the weekend.
The Serbs – many of whom worked in Kosovo’s judiciary before the territory came under the administration of the United Nations in 1999 – said they wanted to set up their own court.
Kosovo’s government unilaterally declared independence from Serbia on February 17 and has since been recognised by many Western countries.
Serbia and Kosovo Serbs say the declaration of independence by Pristina is illegal.
Two days after the proclamation, Kosovo Serbs torched two border crossings with Serbia and have since staged a series of other protests.
Russia, which opposes Kosovo’s independence move, said on Monday that the clashes stemmed from from Pristina’s decision to secede from Serbia.
“The rise in tension there, above all in the ethnic Serb districts, is a direct consequence of the unilateral declaration of independence by Pristina and the non-acceptance of this illegitimate step by Serbs living in Kosovo,” a statement by the country’s foreign ministry said.