Warning Nato not to send ground troops to the region, President Yeltsin said on Friday: "I told Nato, the Americans, the Germans, don't push us towards military action."

President Yeltsin has threatened "a European war for sure - and possibly world war" if Russian demands are not met.

Rob Watson reports from Washington: "Russia has been making increasingly hostile noises"

But the US has chosen to play down differences with Moscow, with plans for a top-level meeting to defuse the crisis.

The American Government is under increasing domestic pressure to consider the use of ground forces, a move Washington has so far ruled out.

A group of congressmen from both main parties has written to President Clinton, saying that to achieve all its objectives, Nato should be urged to plan additional missions, including sending troops into Kosovo should air strikes fail.

The congressmen have just returned from a visit to Europe with the US Defence Secretary, William Cohen.

Human shield protects bridge

Nato's 17th night of bombing raids came at the end of Orthodox Good Friday, a date which Serbia had suggested should be marked by a ceasefire.

(Click here for a map showing Nato's latest strikes).

Instead, for the second night in a row, thousands of Serbs formed human shields to protect key bridges from attack, according to Serbian media reports.

Serbian television showed hundreds of Belgrade residents assembled to discourage air strikes on a city bridge as the city came under attack from Nato planes.

Similar gatherings were reported at bridges around the country and around Serbian TV's own Belgrade transmitter.

Serb media reported that five explosions shook Belgrade late on Friday.

According to a private Yugoslavian news agency, Beta, Nato jets damaged a television transmitter near Kosovo's capital Pristina, knocking out reception in a wide area.

A spokesman for Nato said that poor weather prevented many planes from attacking their targets.

The United States says it is sending six more F-15E fighter jets to Europe for use in the Nato campaign and is leaving a ship with a hospital on it in the Mediterranean to help with refugees.

And at least 24 AH-64 Apache attack helicopters currently stationed in Germany are due in Albania in the next few days.

Albanian border reopens

A convoy of some 1,500 people crossed into Albania late on Friday over a previously closed border - although it was unclear if this meant the border had reopened.

Amid the bombing, Serbs celebrate Easter

The refugees, who were reported to be from one village near the Kosovo capital Pristina, said their homes had been surrounded by Serb forces who ordered them to leave.

It was the first major movement of Albanians from Kosovo since Yugoslavia announced the border was closed three days ago.

Meeting to defuse tension

On Friday, President Yeltsin said Russia could not allow Nato to ''seize'' Yugoslavia and turn Kosovo into a protectorate.

The BBC's Brian Hanrahan: The prospect of Russian military involvement has set alarm bells ringing

Moscow has previously said it would not consider military involvement in the Balkans in any circumstances.

The US Secretary of State Madeleine Albright and Russian Foreign Minister Igor Ivanov will meet in Oslo on 13 April to discuss the crisis.

According to the BBC Moscow Correspondent Andrew Harding, Mr Yeltsin's comments were probably designed more to appease domestic critics than to alarm Nato.

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• Refugees 'lost' in Kosovo

The UNHCR says the number of people who have fled Kosovo since 24 March, when Nato began bombing Yugoslavia, is now more than 620,000.