A spokesman said there were now fewer than 2,000 Serbs left in and around the capital, Pristina, out of a pre-war population of some 40,000.

Many of those who remain are the elderly and the infirm.

UNHCR spokesman Ron Redmond called on ethnic Albanian leaders to restrain those bent on revenge for Serb acts of repression.

Ron Redmond: "Somwhere between 30,000 and 50,000 Serbs are left in Kosovo"

In the latest incident, two elderly Serb women were shot through their front door after a series of threats.

The remaining Serbs have little freedom of movement. Unable to use the shops or go out, many are relying on food parcels delivered by Nato peacekeepers.

He said there had been at least nine murders and seven serious assaults in the city last week.

'Disgusting persecution'

He also said it was unlikely that those left were involved in the persecution of ethnic Albanians, "but that doesn't seem to matter to the thugs who are now terrorising them".

Paul Wood: The UNHCR are sounding a warning over the plight of the Serb minority

"Disgusting" tactics including intimidation, forced expulsions from apartments, beatings and murders have created an unbearable atmosphere for the Serbs, forcing them to live in constant fear, he said.

He also said that conditions for those who remain have noticeably worsened in the past few weeks.

The BBC's correspondent in Pristina, Paul Wood, says international officials know they are losing the battle for a multi-ethnic Kosovo, and some believe that drastic measures may now be needed.

The UNHCR's Balkans envoy Dennis McNamara has raised the prospect of linking aid to the province to efforts by ethnic Albanian politicians to restrain the violence.

"How can we bring in rebuilding equipment for 50,000 homes when we pass down the road and watch them burning down perfectly good homes in the same area?"