UN police in Kosovo have been forced to withdraw from the Serb stronghold in northern Mitrovica after riots in which more than 130 people were injured.
French Nato troops have fired warnings shots, hours after a Ukrainian policeman died from wounds suffered in clashes with Kosovo Serbs in Mitrovica.
About 70 Serb civilians were wounded in the town as well as 63 members of the UN police and Nato-led peacekeepers.
He was the seventh officer killed while serving with the United Nations mission since it began work in Kosovo in 1999.
Rioters threw stones petrol bombs, grenades - as well as firearms - international forces say.
More than 130 people were hurt in rioting after the UN took control of a courthouse seized by the Serbs.
Nato peacekeepers moved into the area and fired a stun grenade on Tuesday when Serbs began throwing stones.
We are very sad. The Kosovo institutions and government send condolences to the family and to his country Hashim ThaciKosovo Prime Minister The protesters were described as high-school students.
French and Spanish soldiers with the K-For force were stationed at the town's main flashpoints in an attempt to prevent a repeat of the previous day's violence.
Bridges over the Ibar river that divides the Serb north from the ethnic Albanian south were closed.
The Ukrainian officer who died had been part of a special unit which had moved in to the courthouse, arresting more than 50 Serbs.
He had suffered shrapnel wounds from a hand grenade.
There have been regular protests in Mitrovica since Kosovo declared independence from Serbia last month.
Kosovo Prime Minister Hashim Thaci told reporters: "We are very sad. The Kosovo institutions and government send condolences to the family and to his country."
'Lethal means'
The UN says 41 policemen are still being treated for their injuries.
Eleven French officers have been flown home for treatment. Ukrainians and Poles are also among the wounded.
Doctors say a Serb demonstrator who was shot in the head is in a coma, fighting for his life.
Nato admitted its troops had used "both lethal and non-lethal means" - but had only shot in the air.
Nato admitted its troops had used "both lethal and non-lethal means" - but had only shot in the air.
The clashes began after the UN tried to wrest control of a courthouse seized by the Serbs last week.
Officials in Belgrade have accused the UN and Nato of using excessive force against demonstrators. Russia's UN Ambassador Vitaly Churkin also suggested there had been a lack of restraint.
It is the worst unrest since Kosovo's independence declaration last month, which Serbia says is illegal.
Speaking in Moscow, US Secretary of State Condoleezza Rice called on all sides to refrain from violence and avoid "provocation".
The BBC's Nick Thorpe, who was barred by local Serbs from entering the north of the town on Monday, reports from southern Mitrovica that an eerie quiet has descended on the town after the day's violence.
On Tuesday, Japan became the latest country to recognise Kosovo's independence, joining the United States and a majority of countries in the European Union.
Anniversary
The unrest coincided with the fourth anniversary of rioting in Mitrovica by Kosovo Albanians which drove some 4,000 people, mainly Serbs, from their homes, and left at least 19 people dead, according to UN figures.
Stones, petrol bombs and gunfire were directed at UN troops
The Nato-led K-For has taken over security in the divided town, where Serbs are concentrated on the northern side of the Ibar river.
The violence began after about 100 UN police arrested 53 Serbs occupying a UN court in the north of the city.
Scores of protesters blocked the police vehicles as they tried to leave and rocks and petrol bombs were thrown, according to Kosovo police.
Almost half of those arrested were set free during the violence. UN and Nato vehicles were set alight.
As the situation escalated, UN police were ordered to withdraw, leaving K-For troops to control the situation.
At least 70 Serbs were treated for injuries, including one person with a gunshot wound to the head, according to Kosovo Serb hospital sources quoted by Serbian media and the Associated Press news agency.
Polish police commander Andrzej Matejuk said 27 of the injured UN police were Poles, but their lives were not in danger. Fourteen Ukrainians with the UN police were also wounded.
The French military said 20 French K-For soldiers were injured, eight seriously.
K-For troops backed by armoured cars are now in control of the court building.
'Excessive force'
"I understand that today [Nato-led] forces had to use both lethal and non-lethal means to control the rioting crowd," said Nato's Supreme Allied Commander Europe, John Craddock, on a visit to Afghanistan.
When we were coming out of the compound, the van I was in was stopped by Serbs who trashed it and freed us Dragoljub DrazevicSerb protester In pictures: Mitrovica rioting
Speaking in Brussels, Nato spokesman James Appathurai said rioters had used "Molotov cocktails, grenades and possible automatic weapons".
French spokesman Etienne du Fayet de la Tour told Reuters news agency K-For troops had "used automatic weapons to respond but fired only warning shots... in the air, not into the crowd".
The European Commission voiced its full support for the efforts of the UN administration and K-For to maintain order, saying violence was unacceptable.
Serbian President Boris Tadic accused the international forces in Kosovo of using "excessive force" and warned of "an escalation of unrest on all the territory of the province".
Russia's ambassador to Nato, Dmitry Rogozin, accused K-For of using "disproportionate force... against women and children", and urged an end to the "escalation".
"Given that there are lot of hidden guns in Kosovo, there could be a lot of bloodshed," he added.
Rallies
Many of the protesters who seized the court last week are said to be former staff who lost their jobs in 1999 at the end of the war in Kosovo, when it came under UN administration.
Serbs had staged rallies outside the building for several weeks, preventing ethnic Albanian court employees from crossing the bridge over the Ibar. Tension in the region has risen sharply since Kosovo declared independence.
Last week, Serbs tried to take control of a railway line in northern Kosovo.
In February, some 150 Kosovo Serb police officers were suspended for refusing to take orders from the Kosovo Albanian authorities in Kosovo's capital, Pristina.
Most EU states and the US have recognised Pristina's unilateral declaration of independence.
Serbia - backed by its ally Russia - says the move is illegal.
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