Two Serbs were killed in separate incidents as Nato troops fanned out across the province and discussions continued at the highest level to determine what role Russia should have in the international peacekeeping force.

American and German forces started moving into Kosovo on Sunday - for the Germans, their largest military mobilisation since World War II.

Jeremy Bowen in Prizren: "Firing from a tank covered in flowers"

Russian troops continued to block access to Pristina airport - Nato's first choice for the K-For headquarters - as negotiations went on about their future deployment.

Meanwhile, the first convoy of United Nations humanitarian aid has reached the province's regional capital, Pristina.

In Pristina and the western city of Prizren, Nato forces have been involved in gunfights with Serbs.

In separate incidents:

• British troops shot dead a Serbian special policeman, who is said to have opened fire on them in the centre of the regional capital, Pristina.
• Two journalists were killed south of Pristina.
• One Serb was shot dead and another injured by German troops in Prizren.

Defence Correspondent Mark Laity: "Nato snapping at the heels of the Serbs"

According to British forces, the Serb special policeman they killed was not in uniform at the time of the shooting.

The incident was the first reported violence involving Nato troops since they began entering Kosovo on Saturday.

Later, unidentified gunmen attacked two German journalists near the town of Stimlje 30km south-west of Pristina.

One was killed on the spot, while another died later, according to the German Foreign Ministry.

Confrontation in Prizren

Paul Wood reports: "The final hours before Nato's arrival were filled with terror"

In Prizren, one Serb gunman were killed and another seriously wounded during an exchange of gunfire with German K-For members.

Witnesses said the German soldiers opened fire on the Serbs, after the gunmen began shooting into a crowd from their car.

One German soldier was slightly injured in the shooting.

Bullet holes riddle the Serbs' car

It is not clear whether the Serbs were soldiers or paramilitaries.

BBC Correspondent Clive Myrie reports that the situation in Prizren, where the Germans are establishing their base, is extremely tense and dangerous.

Serbian forces are reported to have gone on a looting and burning spree after dark in ethnic Albanian areas of the city.

Earlier, there were angry confrontations between departing Serb forces, and Albanian residents who had welcomed the Germans into the city.

Armed Serbs tried to block the progress of the Germans, but relented after about half an hour. Up to 5,000 German troops will eventually be based in and around Prizren.

(Click here to see an animated map showing timetable of Serb withdrawal and Nato's planned movements)

Nato positions

Estimates say that about 10,000 K-For troops were in Kosovo by Sunday night and about 7,500 Serbians had pulled out of the province.

BBC Defence Correspondent Mark Laity said the estimates are in line with expectations but that Nato forces are moving so quickly they are sometimes overtaking the retreating troops, increasing the chances for friction.

British airborne and armoured brigades are now secure in the area of Pristina, according to Nato's latest update on Operation Joint Guardian.

As they arrived, they were greeted on the streets by thousands of cheering Kosovo Albanians. But some Serb civilians shouted abuse at the British forces as they passed by.

British heavy forces are continuing to move in. The deployment of French troops has also proceeded during Sunday.

American, Canadian and Italian forces are now taking up positions after crossing the border into Kosovo earlier on Sunday.

A convoy of US tanks crossed from the former Yugoslav Republic of Macedonia on Sunday afternoon, marking the beginning of the deployment of 7,000 American troops.

The multi-national force will eventually number around 50,000.

Serb withdrawals

But despite the massive peacekeeping force rolling across the border, much of Kosovo remains unstable, with reports overnight of sniper fire at the main border crossing-point with Albania near Kukes.

The thousands of Kosovo Albanian refugees waiting to return home are being urged to wait until the K-For troops make the province safe from bombs, mines and other ordnance.

Serbian refugees are continuing to flee Kosovo, with 9,000 reported to have entered Montenegro since the arrival of K-For in Kosovo.

Many Serbs in the province feel that Nato cannot guarantee their safety after the withdrawal of Yugoslav forces, although the force commander in Kosovo, General Mike Jackson, says his troops will act 'even-handedly' in the province.

• Russians refuse to budge
• British troops kill Pristina gunman
• The push into Kosovo in pictures
• Eyewitness: Watching Nato arrive
• K-For: The task ahead