The videotape shows six men in civilian clothes, shot dead shortly after the beginning of the Nato air strikes.

It was taken by wedding photographer Shpepin Bytyci in the town of Djakovica in western Kosovo, on 27 March.

He says the men - three of them belonging to the Davishdama family, including the grandfather, father and son - were shot dead for refusing to leave their homes.

Mr Bytyci, a neighbour, said he risked his life to film the footage of the bodies with Serbian soldiers patrolling outside.

He said that while the men were being executed downstairs, the women and children were herded into a bedroom upstairs.

The families hid with the bodies inside for three more days, too afraid to bury them.

Mother 'saw daughters shot'

This woman told how soldiers demanded money to spare her life

Another woman, from Klina in western Kosovo, told BBC correspondent Matt Frei how two of her daughters were killed by Serb soldiers:

"We were all surrounded and they sent us towards Albania.

"We didn't want to come here. We wanted to stay at home.

"They started shelling, and they killed two of my daughters. One was 15 and the other eight years old.

"Serbian soldiers pushed us all into a ditch. There were thousands of us from 13 villages.

"They threatened to run us over with tanks unless we gave them money. My sister-in-law gave them 5,000 deutschmarks.

Wheels of justice turn slowly

The BBC showed the taped evidence to Clint Williamson, a war crimes prosecutor now working on the ground in Albania.

He said the ethnic cleansing of Kosovo was a crime or event of "such magnitude that everyone in the international community is trying very hard to respond to it, and it is difficult."

"We are working very hard to react to it, and I feel certain that we'll be here as long as it takes."

BBC correspondent Matt Frei says that when it comes to war crimes, the wheels of international justice turn extremely slowly.

The Bosnian war killed about 250,000 people, most of them civilians, but so far only four suspects have been convicted at the International War Crimes tribunal in The Hague.

Our correspondent adds: "There is no shortage of evidence - in one afternoon alone, BBC reporters heard scores of accounts of ordinary civilians, killed by Serbian forces. The difficulty is catching the culprits."