U.N. special police stormed a U.N. courthouse in northern Kosovo on Monday, evicting Serb demonstrators who have occupied the building since last week to protest Kosovo's declaration of independence, AP reported. Thousands of stone-hurling Serbs later gathered near the courthouse in Serb-dominated Kosovska Mitrovica and clashed with riot police backed up by NATO troops, who used tear gas and stun grenades. At least one U.N. vehicle and one NATO truck were set on fire during the riots. Several demonstrators and police officers were injured, witnesses at the scene said. «The situation is quite tense, but police and NATO are out in force,» Besim Hoti, a spokesman for Kosovo's police in the north of the country, said. This was the most serious clash between Kosovo's peacekeepers and the Serbs since majority-ethnic Albanian Kosovo declared independence a month ago. The Kosovo Serbs took over the U.N. court last Friday. U.N. police said 53 Serb demonstrators who occupied the courthouse were arrested in the action early Monday by about 100 U.N. riot police. Witnesses said some of those who were arrested were later released when the Serb rioters stopped U.N. vehicles driving them away.