But the head of the UN World Food Programme, Catherine Bertini, said her organisation had no way of reaching them, and air drops have been rejected as too dangerous.

Rob Parsons reports on "a people systematically uprooted"

The United Nations High Commission for Refugees has warned that hundreds of thousands of refugees are expected to continue fleeing Serbian violence in Kosovo, predicting that the total number of displaced people could reach at least 650,000.

According to the UNHCR, more than 140,000 refugees have left Kosovo since air strikes against Serbia began.

Five thousand arrived in Macedonia on Wednesday, crammed into just three trains. Aid workers say the scenes of refugees streaming in all directions, tired and traumatised are reminiscent of the darkest days at the end of World War II.

Refugees arriving in Albania, Macedonia and Montenegro told stories of seeing relatives and neighbours killed in cold blood.

Independent corroboration is not possible because foreign journalists have been expelled from Kosovo but correspondents say the refugees are telling consistent stories of Serb atrocities.

"The human mind cannot imagine what they are doing there," said Sabri Hajzeri, 30, a painter who was among the first group of refugees from Pristina, Kosovo's capital, to cross into Albania.

US and Kosovan sources are now reporting that two Kosovo Albanian leaders previously feared dead are still alive.

Fehmi Agani, a politician who played a key role in the Rambouillet talks, and Baton Haxhiu, editor of the Koha Ditore newspaper were previously reported by Nato to have been executed at the weekend.

Belgrade says its forces in Kosovo are merely responding to aggression by the KLA and by Nato.

Trapped in valley

Long queues of refugees have formed at the borders of both Macedonia and Montenegro. People are crossing some border points at a rate of 4,000 an hour.

As refugees pour out of the beleagured province, fears are growing over the safety of an estimated 50,000 Kosovo Albanians, who Nato says are trapped in the central Pagarusa Valley by Serbian forces.

Kosovo Liberation Army fighters defending the valley, 50km southwest of Pristina, have been outnumbered by Serbian tanks and heavy artillery, according to Nato. The civilians have no easy escape route.

Nato officials say the weather is preventing air action against Serb forces in the Pagarusa Valley area.

Pristina emptying

According to a Kosovo Albanian living in London, there has been a mass exodus from Pristina.

There are still fears for those left behind

Speaking to BBC News Online, he said that Serb police forces gave Kosovo Albanians in certain parts of the city an ultimatum to leave by 1600 on Thursday.

He said that the movement of refugees from the north of the province towards refugee camps over its southern borders strikes fear into all the remaining citizens and accelerates their own departure.

He was unable to name his sources, but said he had been in telephone contact with people living in Pristina.