U.N. police began returning on Wednesday to a Serb-held town in northern Kosovo where violence involving protesters armed with guns and hand grenades killed a U.N. policeman from Ukraine and wounded dozens of people.

The clashes on Monday in the town of Mitrovica were the worst since Kosovo declared independence from Serbia a month ago.

The United Nations pulled out of Mitrovica in the wake of the clashes with the Serb protesters who occupied a U.N. court house, leaving the NATO peacekeepers in charge. Officials said that additional U.S. troops trained in riot control were sent in as reinforcements.

David McLean, the regional police commander in Mitrovica, said the U.N. police were returning "gradually" and setting up their operation and patrols. He said he expected to restore the mission "as quickly as possible."

The United Nations has accused Serbia of complicity in the violence. Larry Rossin, the deputy U.N. administrator for Kosovo, told reporters on Tuesday in Pristina that "it is clear to us that the violence ... was orchestrated."

At the very least, Rossin said, Serbia's government failed to use its influence to prevent ethnic Serbs in Kosovo from launching the attacks, which left more than 60 U.N. and NATO forces and 70 Kosovo Serb protesters wounded.

Serbia's "interventions or lack of interventions with those who are causing these problems" are hindering U.N. operations in the Serb-dominated region of Kosovo, Rossin said.

"We've never had what we could consider a clear and unambiguous denunciation of this kind of violence from the ministers or indeed any other Belgrade government official," he said.

A senior Serbian government official dealing with Kosovo, Dusan Prorokovic, denied the allegations, saying that "all we have been doing is trying to calm the situation."

On Tuesday, Serbian President Boris Tadic said his country will never agree to Kosovo's independence and that renewed talks under the authority of the United Nations are the only way to reach a compromise.

Predominantly ethnic Albanian Kosovo has been under U.N. control since 1999, when NATO launched an air war to stop Slobodan Milosevic's crackdown on ethnic Albanian separatists.

Serbia, which considers the territory its historic and religious heartland, says Kosovo's declaration of independence was illegal under international law.

Serbia recalled its ambassador to Japan and Canada on Tuesday after the two countries recognized Kosovo's independence. On Wednesday, Croatia, Bulgaria and Hungary said they were ready to recognize Kosovo, becoming the first neighboring countries to Serbia to do so. There was no immediate comment from Belgrade.

Russia strongly opposes Kosovo's independence.

Serb demonstrators traded gunfire with international peacekeepers Monday and attacked them with rocks, hand grenades and Molotov cocktails as police removed protesters from inside a U.N. courthouse.

The policeman from Ukraine who died of injuries sustained by a hand grenade thrown by a protester was identified as 25-year old Ihor Kynal.

"He basically bled to death," said Larry Wilson, the top U.N. police official in Kosovo. "Because of the gunfire it took us almost two and a half hours to evacuate him."

U.N. Secretary-General Ban Ki-moon was "deeply saddened" to learn of the death and extends his condolences to his family and the government of Ukraine, U.N. spokeswoman Michele Montas said at U.N. headquarters in New York. "The secretary-general calls on all parties to refrain from violence and to engage in a constructive dialogue and work together to promote security and stability in Kosovo."

Britain's U.N. Ambassador John Sawers said, "What we saw yesterday showed the lengths to which some people ... in the Kosovo Serb community are prepared to go."

"The great bulk of Kosovo is calm and the majority of the Serb community are getting on with their lives. But there seem to be those who are deliberately stoking trouble in the north of Kosovo because they seem to want to see violence, they seem to want to have a confrontation. That is not our wish," he said.

A Serb demonstrator who was shot in the head remained in a coma. The U.N. in Kosovo said Tuesday that 41 injured U.N. policemen were still being treated.

The top NATO commander in Kosovo said Tuesday the peacekeepers used "appropriate force" and warned that the 16,000 strong force showed it would not give in to violence.

"Don't put us in a position to show it again," Lt. Gen. Xavier Bout de Marnhac said.