Many of them are believed to be in prison in Serbia.

So far the International Committee of the Red Cross has located just under 2,000 people in Serbian prisons, where they are being held mostly on terrorism charges. They are still awaiting trial.

The BBC's Nick Thorpe in Pristina: "At the moment, the demonstrators can only hope that their relatives are still alive."

But another 3,000 are missing, so far without a trace.

With the government in Belgrade still at loggerheads with the international community, the BBC's Nick Thorpe in Pristina says the most that relatives can hope for at the moment is that their men are alive and will one day be allowed home.

'Missing since June'

Once again, Kosovo Albanians are looking to the West for help

One man told the BBC that his brother-in-law had been taken from his home on 2 June by Serbian police but only now has he been given the name of the prison where he is being held.

"The international community doesn't do anything right now," he complained. "They are trying so much to help the Serbs here. They don't do anything about the prisoners."

The demonstrators marched to the United Nations mission.

Promises

They have not heard of their relatives for months

The UN special representative in the province, Bernard Kouchner, spoke to the crowd and promised his full support.

"We will try harder to know about the people," Mr Kouchner was quoted as saying.

"It is against all the laws, human rights and Geneva Conventions... not to say, not to tell the families about their relatives. This is a barbarian way to treat the people," he said.

The UN representative also promised a "strong statement" on prisoners and missing persons.

He told the crowd that he was planning a human rights conference in Kosovo as well as a local forum to look into the issue of missing and detained people.