MITROVICA, Kosovo, March 17 (UPI) -- An explosion Monday injured five international peacekeepers in Kosovo as they stormed a courthouse occupied by Serb protesters, officials said.

Three U.N. police officers and two NATO soldiers were injured by an apparent hand grenade blast.

At least 20 Serbs protesting Kosovo's unilateral declaration of independence were injured when U.N. police and NATO forces stormed and reclaimed the U.N. court building in the ethnically divided city of Mitrovica, Voice of America reported.

The building was occupied Friday by Serb protesters.

About 500 U.N. police, mainly Ukrainian, were involved in the raid, backed by hundreds of French troops. Thousands of Serbs were seen near the courthouse clashing with riot police, backed by NATO troops, who used tear gas and stun grenades to disperse the crowd, VOA reported.

Swedish Foreign Minister and former U.N. Special Envoy for the Balkans Carl Bildt said Mitrovica has become a hot spot because it is a town of separate Albanian and Serb communities.

"I was there in the bridge of Mitrovica. It is a bridge between two societies that have very few (things) in common," he told VOA. "To overcome that division of Kosovo ... this will take a long time. We will need a lot of patience."