Kosovo Serbs clashed with NATO peacekeepers at a Kosovo-Serbia border crossing Tuesday after weeks of tensions in the region.

Four peacekeepers were wounded when protesters threw pipe bombs at them. The solders responded with rubber bullets and tear gas, wounding at least seven Serbs. One Serb was shot when he tried to steal a weapon from a peacekeeper.

Violence broke out when international forces began taking down Serb barricades at a disputed border crossing point. Serbian President Boris Tadic condemned the violence. He said international forces are there to defend unarmed civilians, not to fight with them. But a spokesman for the European Union mission in Kosovo says violence against peacekeepers is unacceptable.

Earlier this month, ethnic Serbs in northern Kosovo blocked roads to protest a decision to put Kosovo customs officials at the Brnjak and Jarinje border crossings.

Kosovo's government has moved to assert control over the north, which is populated primarily by ethnic Serbs who refuse to recognize the government's authority.

The Serbs in northern Kosovo join Serbia in refusing to recognize Kosovo's 2008 declaration of independence.