The Russians - around 200 troops in armoured personnel carriers and trucks - remain in the province despite an assurance by the Russian foreign minister, Igor Ivanov, that they had been ordered to leave the provincial capital.

The troops crossed the Yugoslav border on Friday from Bosnia, where they had been part of the S-For peacekeeping force.

The BBC Corresondent in Pristina, Michael Williams, said the Russians were greeted like a liberating army by thousands of cheering Serb residents of the Kosovo capital when they arrived in the early hours of Saturday morning.

Talbott on Saturday: Harrassed

Serb military police, who are due to withdraw from Kosovo under a UN-backed peace agreement, have sealed off the road the airport where the Russians are camped.

Our correspondent says the Serb population in the city fears Nato, and the arrival of Russian forces may reassure them.

James Robbins reports: "Nato thought the Russians would stop at the border"

It is not clear how long the blockade will remain. Advancing British troops of the Kosovo international intervention force intend to make the airport their headquarters.

At Saturday's Nato briefing in Brussels, Nato commander Wesley Clark said British reconnaisance troops were either "at or on " the airport and the matter would be sorted out "in the fashion that soldiers normally do".

Confusion in Moscow

BBC Moscow Correspondent Andrew Harding says many analysts there believe Russia's generals decided to go it alone and score a quick propaganda victory against the West.

Andrew Harding: "For the Russian government, contradictions and confusion are nothing new"

President Yeltsin has been discussing the development, which breaches previous commitments, with Prime Minister Sergei Stepashin, and his foreign and defence ministers.

Mr Yeltsin also promoted the general who led the column of Russian troops, seemingly contradicting Mr Ivanov's assertion that the matter was a mistake.

Viktor Zavarzin was warded the rank of colonel-general, Itar-Tass news agency reported.

The general had been Russia's representative to Nato, before he was pulled out of Brussels when the bombardment began in March.

Meanwhile, in Moscow, US envoy Strobe Talbott has been continuing talks with the Russian foreign minister to try to resolve differences over Russia's role in the Kosovo peacekeeping operation.

The BBC's Richard Lister on US embarrassment and irritation at developments

After 90 minutes of talks on Saturday morning, correspondents say a harassed-looking Mr Talbott told reporters that the talks would resume later in the day and would continue on Sunday.

The talks broke down on Friday, but Mr Talbott was recalled to Moscow in mid-flight when it emerged that Russian forces had entered Yugoslavia.

US acceptance

Scenes of Serb jubilation when the Russians arrived in Pristina

Russian officials say US President Bill Clinton and President Yeltsin will hold direct talks on Sunday by phone.

The US said on Friday it had accepted an explanation of how the Russian troops came to be in Kosovo from Foreign Minister Igor Ivanov.

"As Foreign Minister Ivanov has said, it was an unfortunate mistake and the troops will be withdrawn immediately," Presidential spokesman Joe Lockhart said on Friday.

"We're pleased that they've agreed to rectify the situation. The constructive talks towards determining Russia's role in this peacekeeping force continue with Strobe Talbott in Moscow."