PRISTINA, March 18 (IslamOnline.net & News Agencies) - At least 22 people were killed and more than 500 injured as the U.N.-administered Serbian province of Kosovo was swept by its worst violence between ethnic Albanians and Serbs in three years that also left U.N. vehicles in the capital Pristina charred.

The clashes came after reports that two Albanian children drowned in a river and one was missing after being chased by a group of Serbs with a dog in the town of Kosovska Mitrovica, Agence France-Presse (AFP) reported on Thursday, March 18.

The incident triggered crowds of angry ethnic Albanians attacking towns and villages on Wednesday, March 17.

A curfew was imposed on the town, Kosovo's third largest, as the violence spread throughout the province of 1.8 million Muslims and 80,000 Serbs, while U.N. Secretary General Kofi Annan called on all parties to halt the violence.

Meanwhile, the Serbian police was put on maximum alert along its internal border with Kosovo, the interior ministry said Thursday.

Demonstrations took to the streets in the Serbian capital Belgrade in which several policemen were injured overnight Wednesday, Interior Minister Dragan Jocic said.

Hundreds of Serbs tried to set fire to a mosque in central Baghdad something which they managed to do as police withdrew. The fire was put out an hour later after the police dispersed the protesters.

Another mosque was also set ablaze in the Serbian city of Nis after a protest by more than 2,000 people, AFP added.

On the other hand, an Orthodox church in Obilic, near the capital of Kosovo, was in flames Thursday, Angela Joseph, a spokeswoman for the U.N. mission in Kosovo (UNMIK), said.

U.N. war crimes prosecutor, Carla Del Ponte, voiced his concerns about clashes in Kosovo as a warning signal that the ethnic conflict between Serbs and Albanians could escalate, AFP reported.

"It is an alarm sign that this armed conflict is still ongoing," Carla Del Ponte told journalists on the sidelines of a U.N. human rights meeting.

The chief prosecutor at the International Criminal Tribunal for the former Yugoslavia (ICTY) said she hoped that the NATO-led peacekeeping force in the Serbian province could prevent an escalation "because there is a real danger."

Meanwhile, chairman of Bosnia's collective presidency Sulejman Tihic expressed fears Thursday that the new wave of violence could destabilize the volatile Balkans region, a Bosnian news agency reported.

Clashes "could destabilize the entire region," Bosnian Serb news agency SRNA quoted Tihic as saying.

The riots sparked series of angry protests in Serbia in which several policemen were injured.

On the other hand, Bosnian Serb Prime Minister Dragan Mikerevic condemned the violence in Kosovo and blamed the local Albanian authorities and international administrators.

He said the "actual authorities in the province and the international community are carrying the biggest responsibility" for the casualties.

Russia, for its part, condemned on Thursday the violence and urged rapid steps to avoid an escalation in the entire region.

"We strongly condemn the instigators of the riots in Kosovo and demand that they be put to a halt immediately, as they could lead to an explosive situation in the province and region as whole," Russian foreign ministry spokesman Alexander Yakovenko said.

Russia, a historical ally of Serbs which vociferously opposed the 1999 NATO intervention in Kosovo, has remained skeptical about the international community's role in Kosovo.

Meanwhile, NATO ambassadors met on Thursday for emergency talks on Kosovo violence as it declared it had summoned 100 to 150 U.S. troops reinforcements for the province, an official said.

"It's an extraordinary council," said the official, referring to a meeting of the North Atlantic Council called by NATO Secretary-General Jaap de Hoop Scheffer.

"It's more for an exchange of views. Some measures have been taken, and at this point there is nothing more we can do."

It is now patrolled by 17,000 troops of a multinational force led by NATO, plus 10,000 U.N. and local police.

NATO staged a bombing campaign on Belgrade in July 1999 to force the Serbian army out of the province in a campaign to end a crackdown on the ethnic Albanian majority.

Discussions addressed emotive issues such as missing people in Kosovo, mostly ethnic Albanians, and the future of more than 100,000 mainly ethnic Serbs who fled after troops withdrew. It did not, however, tackle the issue of Kosovo's final status.

• Kosovo Violence in pictures