The peacekeepers, part of the Nato-led K-For operation, are trying to prevent hundreds of Kosovo Albanians from crossing a bridge across the Ibar river into the Serbian part of town.

The BBC's Orla Guerin reports: "The idea of a multi-ethnic Kosovo is being put to the test"

The BBC's Paul Wood who is at the scene says Albanians singing and chanting slogans were pressed against the thin line of French troops. Some scuffles broke out.

Overnight a rocket propelled grenade was fired from the Albanian to the Serb side and a number of shots were fired in the vicinity of an Albanian cafe.

Ethnic flashpoint

Mitrovica has the highest Serb population in Kosovo, with as many as 20,000 living in the Serb part of the city. It is considered one of the main potential flashpoints in the province.

On Saturday French troops used armoured cars to close the bridge and keep the Albanian and Serb demonstrators apart after clashes broke out.

The trouble began when Kosovo Albanians assembled for a political rally at the bridge. When their leaders failed to turn up, the Kosovo Albanians tried to cross the river, but were confronted by the Serbs on the other side of the bridge, some chanting provocative slogans.

The heavily-armed French peacekeepers tried to defuse the angry crowd as they hurled stones at each other.

At least four Kosovo Albanians were detained, and some handcuffed to lampposts by the French troops. Some of the protesters were injured, though none seriously.

Saving lives

A number of arrests were made on Saturday

The French Nato commander in the town, Brigadier General Bruno Kush, told the BBC it would have been dangerous to let the Albanians pass.

"Our first priority is to save lives. If we had allowed them through, some might have been lost," he said.

Nato had been hoping both sides would eventually sign an agreement on freedom of movement in the town, but a French Nato spokesman admitted there was now little chance of a deal.

Most of the town's shops and factories as well as the university and hospital are located on the Serbian side of the river.

Many Kosovo Albanians say they were evicted from their homes on the Serb side during the war and both the Serbs and the French peacekeepers have prevented them from returning.