More than 200 officers from at least 10 countries took up their duties on Sunday as part of a United Nations policing operation.

The civilian police force is intended to work alongside a specially-recruited multi-ethnic local force of 5,000.

Critics of the scheme say the operation is too small and is being deployed too slowly to control the violence in Kosovo.

So far, 500 of the planned 3,100 officers have undergone training.

Clashes continue

The difficulties the new police will face were highlighted on Sunday by a second day of clashes between Kosovo Albanians and French peacekeepers.

Scuffles broke out in the northern town of Mitrovica as troops from the Nato-led K-For operation stopped Kosovo Albanian demonstrators crossing a bridge into the Serbian part of the town.

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

K-For has more than 35,000 troops in Kosovo, but their representatives argue that as a military force, their primary job is not to act as police.

The new force will eventually take over investigating crime, patrolling streets and controlling traffic.

But the main European envoy for Kosovo, Finnish President Martti Ahtisaari, has questioned whether the operation will be sufficient to maintain law and order.

He told Finnish radio last week: "I'm afraid the role of the international police force hasn't been properly thought out. The idea that 3,000 police could maintain order ... is out of this world."

Stand-off

The continuing violence in Mitrovica underscored these concerns.

The town 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.

Reports said that on Sunday about 150 young Albanian men threw stones at troops blocking the bridge with an armoured personnel carrier.

They taunted the peacekeepers over their refusal to allow them to cross, waving Albanian flags and cursing the soldiers as "terrorists". At least one protester was arrested in the scuffles.

Captain Bertrand Bonneau, the commander of the French K-For contingent, said: "Our goal is to cool down the tension. We try to understand they are impatient. We must remain vigilant."

Mitrovica is considered a major flashpoint in Kosovo

The commotion was reported to have died down by mid-afternoon and the bridge was re-opened to pedestrians.

The incident followed a larger confrontation on Saturday, when up to 1,000 Kosovo Albanians tried to cross the bridge. Hundreds of Serbs were waiting on the other side.

The peacekeepers forced back the crowd, arresting four people.

In another incident, Nato officials said French troops opened fire when gunmen using small arms and grenades attacked a Serb residential district in the town. Officials said one attacker was arrested.

Ethnic violence

Nato peacekeepers also reported several grenade attacks against Serbs across Kosovo on Saturday night, including one in Mitrovica.

The BBC's Paul Wood reports on the tense relationship between Nato peacekeepers and the KLA

In Pristina, a Serb bar was hit by a grenade attack, wounding three Serbs.

Another grenade attack in the capital early on Sunday left one suspect wounded. He was being questioned, Nato officials said.

State-run news agency Tanjug said four Serbs in the village of Gornja Brnjica, north of Pristina, were wounded on Saturday by shots fired from a passing car.