Survivors of reported massacres have described to the BBC how refugees were robbed before being gunned down.

Others say that Serb doctors took blood from men who were then massacred and their bodies burned.

(Click here to see a map of refugee movements to date)

The BBC's Ben Brown: "Too late for the hundreds, possibly thousands, killed in atrocities"

One organisation working in the Albanian camps, Human Rights Watch, believes it has uncovered details of a recent massacre of young men in a Kosovo village.

Spokesman Andre Lommen told the BBC what allegedly happened.

"Serb forces...basically went from tractor to tractor to tractor demanding money from people, beating a couple of people up," he said.

"Those who didn't have money in several cases got executed right at the spot."

This man only has a ring to remind him of his dead brother

He said refugees had witnessed "30, 60 or 70 bodies" lying in the road, while others had "seen people shot in front of their eyes".

A Kosovo Albanian man who said he survived that massacre despite being shot through the leg told how his relatives were murdered.

"They took my brother off the tractor and shot him dead, then they shot my uncle too," he said.

Another man recounted an earlier reported atrocity in which blood was forcefully taken from a group of Kosovo Alabanians.

Blood theft: A refugee shows how refugees were lined up

"Doctors lined the men up and took blood from their arms to go into the Serbian blood bank," he said.

"The men began staggering around because they were so weak when the blood was taken from them, then they were rounded up into a group and shot with machine guns."

He said the Serbs then poured petrol over the bodies and set fire to them.

Shelling continues close to the border

Human rights investigators are collecting individual testimony in painstaking detail so that in the event of any future war crimes trial there will be no shortage of evidence.

And the UK Foreign Office has already named high-ranking officials that are believed to be guilty of war crimes.

These include Yugloslav President Slobodan Milosevic, Interior Minister Vlajko Stojilkovic and Major General Circic, head of the Serbian secret service (RDB).