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The United Nations refugee agency, the UNHCR, says the refugee situation is reaching nightmare proportions.

United States President Bill Clinton said on Friday that Nato forces could not allow Yugoslav President Slobodan Milosevic to hold onto a Kosovo emptied of its people.

Nicholas Witchell reports: Now only "quite a good chance"

"There's no doubt that what Mr Milosevic wants to do is to keep the land of Kosovo and rid it of its people,'' Mr Clinton said. ''We cannot let this happen with impunity."

The president said the humanitarian situation in Kosovo was "grave" and urged greater international help in dealing with the escalating crisis.

'Situation out of control'

The United Nations estimates more than 180,000 have crossed into Macedonia, Albania and Montenegro in the last 10 days.

Aid agencies are warning of a humanitarian disaster not seen in Europe since World War II as the organised expulsion of Kosovo Albanians by Serb forces continues without respite.

Ben Brown reports: "They have exchanged one kind of hell for another"

The authorities in Macedonia say the country can no longer cope with the refugee influx and are appealing for international help.

The Albanian Government has warned of a catastrophe. "The situation is out of control," Information Minister Mussa Ulqini said.

Emma Bonino, the European commissioner for humanitarian aid, has called for safe havens to be set up to protect the Kosovo Albanians.

She says an international military presence is needed in Kosovo to protect the tens-of-thousands of Albanians forced from their homes.

Milosevic defiant

The Serbian authorities have begun collecting evidence for proceedings against three US soldiers captured by the Yugoslav army on the border between Macedonia and Kosovo.

Yugoslavia has said the three will be treated humanely.

And according to the official Yugoslav news agency, Tanjug, Mr Milosevic has asked Russia for military aid during a meeting in Belgrade with Russian MPs.

So far Russia has ruled out giving military support. But President Milosevic remained defiant. "We will defend our country,'' he said. ''If we have assistance, then we will defend it more easily, and if we have none, then defending it will be harder, but we will definitely defend it."

Forced march

More than 25,000 Kosovo Albanians have been forced onto trains in recent days and sent to the Macedonian border, joining crowds of refugees who have got there on foot.

UN spokesman Fred Eckhard said people were being rounded up in what appeared to be a "deliberate and systematic policy to railroad large sections of the population into exile".

Forced out of the carriages two miles from the border and robbed of their last possessions and documents they are then ordered to walk the rest of the way to the former Yugoslav republic of Macedonia.

Aid agencies say they do not know how they will cope. Up to 10,000 men, women and children are gathered in fields next to the border.

There are no shelters - they sit on bare grass, huddled in groups of up to 20, trying to keep warm and shelter from the rain.

Correspondents say sanitation is non-existent, children are starving and the elderly barely have the strength to go on.

Albania 'overwhelmed'

A woman is carried to the border in a wheelbarrow

A further 11,000 refugees arrived overnight in the northern Albanian town of Kukes where aid workers say the situation is critical.

Refugees crossing into Albania say Serb paramilitary forces have systematically emptied Pristina at gunpoint over the last 48 hours and driven them towards the border.

Albanian residents have taken some refugees into their homes, but many are sleeping in the streets and there is a shortage of food and water.

The Albanian Government is reported to have announced the closure of all schools in the border region to provide accommodation.

Sixteen plane loads of relief supplies have arrived in the Albanian capital, Tirana.

B-1 bombing starts

Nato announced on Friday that American B-1 bombers had been used in the onslaught for the first time.

The bombing missions focused on reducing President Milosevic's dwindling fuel supplies.

Milodrag Popovic, Deputy Info Minister in Belgrade: "Under the Geneva Convention, you are not allowed to bomb our country"

But bad weather continued to hamper raids against Serb forces.

British defence officials are warning of a possible coup attempt in Montenegro backed by President Milosevic in Belgrade.

Montenegro is part of the Yugoslav Federation but the republic's leadership has distanced itself from Belgrade's ethnic cleansing policy.