Only an estimated 10,000 of the 300,000 civilians driven from their homes by the Serbs have started to return. The rest, they say, are too afraid of the presence of the Serb police.
With temperatures dropping fast, the extent of the refugee crisis is seen as critical to the West's decision on whether to launch air strikes against Serb forces.
The latest UN refugee figures from Kosovo paint an alarming picture of "spillover" from the province, which threatens to destabilise the region. The prevention of destabilisation may provide the legal basis for Nato intervention in Kosovo under the existing Security Council resolutions.
Almost one-third of those who have fled their homes in Kosovo have now left the province and are either in Serbia, in neighbouring former Yugoslav states or in Albania. Most of the refugees - about 45,000 - are believed to be in Montenegro, 20,000 in Serbia, 18,000 in Albania, 6,800 in Bosnia and 1,000 in Macedonia.
The European Union's humanitarian aid office is now beginning to send aid to Montenegro to help the authorities to cope with the influx. Montenegro is already dealing with 30,000 refugees from Bosnia.
The UN fears the number trying to enter Albania, an increase of 4,000 in only five weeks, is putting immense strain on the local population, which is already facing an economic crisis and political instability. Most of the 300,000 displaced people are thought to have taken refuge with relatives in the towns and villages east of the Kosovo region of Drenica, the stronghold of the armed separatists of the Kosovo Liberation Army.
This is the region where the worst atrocities have been perpetrated. But the UNHCR is seriously concerned about 50,000 people who are believed to be camping out in the hills near Drenica, sheltering under makeshift plastic tents.
The refugees are so afraid that when a UNHCR convoy arrived near the village of Golubovac on Tuesday with supplies of baby milk, food and blankets, villagers who had fled Serb shelling two weeks ago refused to come out of their hiding places.
"The Serb police presence is terrifying for these people" said Maki Shinohara, of the UNHCR.
European governments fear an influx of refugees into the EU. The numbers of asylum-seekers from Kosovo has risen sharply and the problem was discussed recently by EU home affairs experts on the secretive K4 committee.
Franco-German plans for a refugee return programme, partly in response to the threat of an influx, have raised fears among human rights campaigners of a repeat of the Western policy in Bosnia of creating so-called "safe areas", where civilians would be left to the "protection" of the Serbian police or the Yugoslav army.
"You would be driving the very people you want to protect into the arms of the people who have been slaughtering them," said Lotte Leicht, of Human Rights Watch, the New York-based organisation.