Repeated power cuts caused by Nato raids have severely restricted water supplies in the Serbian capital and the northern city of Novi Sad.

But as the alliance air campaign enters its third month, a senior United Nations humanitarian official, who has just left Kosovo, says the evidence of widespread ethnic cleansing there is worse than expected.

Diplomatic efforts to reach a political settlement to the conflict are not expected to restart until Thursday when the Russian and European envoys travel to Belgrade.

Belgrade water shortage

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.

Yugoslav Foreign Ministry Spokesman Milislav Paic: "These allegations are completely unfounded."

"Every effort is being made to restore power supply to priority users to alleviate the humanitarian disaster being caused by Nato," the company said in a statement carried by Tanjug news agency.

One pro-government television station says 70% of Serbia is now without electricity and Belgrade is reported to be down to its last 10% of water reserves.

'Gigantic crisis' in Kosovo

The leader of a UN humanitarian mission to Kosovo has been speaking after a three-day visit to Kosovo where he said there is need for urgent humanitarian assistance for at least half a million displaced ethnic Albanians.

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

The BBC's Clive Myrie: "The whole truth may never come to light"

Speaking earlier in Montenegro, he said there was enough evidence to confirm there has been an attempt to displace "a shocking number" of civilians.

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

Overnight refugee exodus

Relief workers in the former Yugoslav Republic of Macedonia are struggling to cope with 20,000 new refugees who crossed over from Kosovo over the weekend.

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

The BBC's Orla Guerin: "For some, the border is the last hope"

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

A UNHCR spokeswoman said the latest influx of refugees appeared to be the result of "a final push by the Serbs to empty some parts of Kosovo".

(Click here to see a map of the refugee movements and of the most recent reported air strikes)

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

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.

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 Finish President Martti Ahtisaari.

Dissent among Serb forces has been felt in southern towns

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

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.

This appears to echo a statement made on Sunday by US Secretary of State Madeleine Albright, who said Nato might permit a "symbolic" Serb force in Kosovo.

Russia disagrees with Nato on the issue of airstrikes against Yugoslavia, but Mr Ahtisaari said on Saturday that on the main issues, Russia and the major western powers "see eye to eye."

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.

Sources in the opposition Democratic Party say in the town of Krusevac, the wives and mothers of army reservists took to the streets to protest against the return to Kosovo of their sons and husbands.

• General sent to stop troop mutiny
• Allies 'united' on Kosovo troops
• Milosevic must go, says Montenegro president
• War crimes investigator sent to Albania

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