William Walker: "I think it's pretty hard to visualise this being a mistake."

William Walker said it was clear who they were as they were travelling in the bright-orange vehicles used by the monitors.

The two men - a Briton and his locally-recruited interpreter - were in a convoy with Serbian police when they were hit. They were not seriously injured.

It was the first such incident since the monitors from the Organisation for Security and Co-operation in Europe (OSCE) were deployed in the disputed Serbian province last year.

The incident happened as the group were on their way to mediate in a confrontation between ethnic Albanian rebels and Serb forces in the western region of Pec.

Mr Walker said: "What I've heard so far about the firing, it was not just one shot or two shots, it was sustained firing. That would lead me to believe that it was a deliberate shooting."

He pointed out that the monitors drove distinctive vehicles and that everyone in the area had been informed that they were going out on patrol.

High-powered rifle

Jacky Rowland in Pristina: "There have been questions over the future of the mission from the very moment it began."

The KVM members had been moving along a ridge near the town of Decani in a convoy with Serb forces when high-powered rifle fire pierced the windows of their armoured vehicle.

A spokesman for the international monitoring mission said the shots appeared to come from a sniper in territory held by the ethnic-Albanian Kosovo Liberation Army.

KLA territory: Probably source of the gunfire

The spokesman stopped short of accusing the KLA and would not say whether he thought it was a deliberate attack.

UK Foreign Secretary Robin Cook said he was shocked and concerned about the shooting of two members of the KVM.

"KVM members, of whom 110 are British, operate in unpredictable and demonstrably dangerous conditions. I pay tribute to their courage and professionalism", he said.

Ceasefire in danger

There has been fighting elsewhere in Kosovo with both sides reporting casualties.

The BBC's George Eykyn: "A growing threat of all out war in Kosovo this spring"

The Serbs say they have killed 15 ethnic Albanian rebels in the Stimlje region, south of Pristina.

If confirmed, it would be the second-highest death toll in a single clash since an informal ceasefire was agreed in October.

Albanian sources say the Serbs bombarded villages in the area with artillery fire, killing seven people.