The Chief of the Defence staff, General Sir Charles Guthrie, said that mass graves were "continually" being discovered, with evidence from refugees and surveillance.

"There are reports that thousands of young men have been murdered," he said.

There were stories from refugees of whole villages being massacred while other reports suggested that 50 men were shot dead in one incident, the general said.

Friday's briefing included a live video link to Brigadier Tim Cross, commanding troops in the refugee camps in Macedonia.

Vanessa:'We were kicked out of our homes'

He was joined by a 15-year-old refugee called Vanessa, who said her family and neighbours had been removed from their home by Serbian military police.

"They told us to go to Albania because Albania is our place," she said.

Brigadier Cross said he was very proud of his troops, who had never lost sight of the fact that everyone had to be treated as an individual, despite the huge number of refugees.

He said stories "from just about every family in the fact they have lost relatives, been separated from children, from parents, brothers, sisters, uncles and aunts frankly, is a tragedy in itself.