Scores of men had terrible bruising to their backs and arms, which they said had been inflicted on them by Serbian paramilitaries.

UN officials estimate about 20,000 have crossed into the former Yugoslav Republic of Macedonia at Blace since Saturday.

Aid workers say Serbs may have begun a final push to empty parts of Kosovo.

And the leader of a UN humanitarian mission who has just left Kosovo, says the evidence of widespread ethnic cleansing there is worse than expected.

The BBC's Paul Royall: "The journey is not over yet"

Sergio Vieira de Mello told the BBC the scale of the crisis in Kosovo was "gigantic".

The Yugoslav ambassador to the UN, Vladislav Jovanovic, denied ethnic cleansing was official policy, but pointed out that a state of war existed in Kosovo with both sides involved in hostilities.

And as the alliance air campaign enters its third month, Nato bombers have again hit power facilities in Serbia, causing shortages of electricity and water.

John Simpson in Belgrade: People here are frightened and angry

Repeated power cuts have severely restricted water supplies in the Serbian capital and the northern city of Novi Sad, although Nato has denied targeting water supplies.

Belgrade's water authority has appealed for people to cut consumption until supplies can be restored, and the state-run electricity company has pleaded for patience.

Urgent help needed

Sergio Vieira de Mello: Reality in Kosovo was worse than I thought

Speaking after a first UN visit to Kosovo, Mr de Mello said there was a need for urgent humanitarian assistance for hundreds of thousands of displaced ethnic Albanians within Kosovo.

He said he had travelled extensively throughout Kosovo, although the Serbs had prevented him from visiting a number of areas.

He said there was enough evidence to confirm there has been an attempt to displace "a shocking number" of civilians.

"We have seen many of them in the last three days, receiving very little support. Certainly nothing from the international community," he said.

The BBC's Orla Guerin: Indications of a systematic attempt to flush out the population

Altogether about two-thirds of the 1.8 million Kosovo Albanians are now believed to be outside their homeland.

Meanwhile, in Kosovo itself an unknown number - possibly hundreds of thousands - are either on the run or have been moved to designated areas by the Serbian authorities.

This is thought to leave only a small minority of Kosovo Albanians still living in their pre-war homes.

Exhausted refugees

Relief workers in Macedonia are struggling to cope with the new influx of refugees.

The Macedonian authorities had attempted to bus thousands of them straight to Albania, but relented after holding them at the border for 12 hours.

Representatives of the UNHCR protested, saying the people were mentally and physically exhausted.

Its special envoy, Dennis McNamara, said the Macedonian Government would have been in breach of existing agreements if they had refused to let the refugees stay.

Hundreds of male refugees from Kosovo have also been crossing the border into Albania. They say they had been held for weeks in prison, and then suddenly released without explanation.

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

UN officials say the men were traumatised by beatings at the hands of Serb paramilitaries. They were also showing signs of malnutrition, the first seen among refugees in the current conflict.

Diplomacy on hold

The diplomatic push to bring an end to the conflict is not expected to regain pace until Thursday. Russian envoy Viktor Chernomyrdin is reportedly hoping to visit Belgrade accompanied by Finnish President Martti Ahtisaari.

Mr Ahtisaari, representing the European Union, and US Deputy Secretary of State Strobe Talbott are due to travel to Moscow for talks on Wednesday with Mr Chernomyrdin.

On Monday, Mr Chernomyrdin said he had managed to persuade his Western counterparts to allow Yugoslavia to allow some troops to stay in Kosovo as part of a negotiated peace deal.

Anti-war rallies

General Nebojsa Pavkovic, the Yugoslav commander of the Kosovo campaign, spent Sunday in the Serbian town of Raska, where many dead and wounded Serbs have arrived over the past few days.

He promised those men who were sick or needed to provide for their families could stay at home but others would still have to go to Kosovo to fight.

His concessions are reported to have done little to placate the more than 1,000 protesters reported to be rallying against him.

• Nato denies targeting water supplies
• UN accuses Serbs of ethnic cleansing
• General sent to stop troop mutiny
• Allies 'united' on Kosovo troops
• Analysis: The war for hearts and minds

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