UN police stormed a courthouse in northern Kosovo Monday to remove Serb protesters, setting off clashes that injured more than 200 international peacekeepers and demonstrators. Hundreds of Serb protesters outside the UN courthouse hurled rocks and hand grenades at UN police and NATO troops, who responded with tear gas and stun grenades. It was the worst violence in Kosovo since its majority ethnic Albanians declared independence from Serbia a month ago. Protesters in the Serb-dominated town of Kosovska Mitrovica had occupied the courthouse since Friday to protest the declaration, which Kosovo's Serb minority fiercely opposed. The riot posed a direct challenge to NATO, the United Nations and Kosovo's fledgling European Union justice mission, underscoring fears in the West that Kosovo could be heading for ethnic partition one month after breaking away from Serbia. A UN spokesman said the riot “crosses one of the red lines that had clearly been articulated by the UN to the leaders of Kosovo Serbs in the north and to officials in Belgrade.” But Serbia blamed the UN and NATO for heavy-handed action and increased the level of security on its borders, warning that the highly volatile situation risked provoking a fresh Albanian action against Kosovo's 120,000 minority Serbs. The protesters have been trying to take control of local institutions that have been run by the UN since the end of the war in Kosovo in 1999. __