Eyewitnesses said a Russian plane fired a missile at a column of cars and buses near the border with the neighbouring republic of Ingushetia.

The refugees had gathered after reports that the Russians would open the border to allow them to leave. They were hoping to escape the continuing Russian strikes on the breakaway republic.

BBC News' Orla Guerin: Russia warning that Chechnya is an internal matter

Russian troops allowed some wounded people to cross into Ingushetia where they spoke to journalists. Many more refugees have been turned back.

Reuters correspondent Maria Eismont spoke to eyewitnesses. She said: "I heard Chechens saying about 50 were killed, but I can't confirm that number and neither could these people I have talked with.

"They said there were a lot of wounded - how many, I don't know."

'Terrorists targeted'

Reuters correspondent Maria Eismont in Ingushetia

Russian officials continue to insist their forces are striking only at terrorist bases.

But Chechen doctors working for the international humanitarian organisation, Medicines du Monde, say that is not true.

A Moscow based spokesman for the organisation said: "There are a lot of civilian victims, dead and injured people. They are bombing hospitals, schools, markets, houses. One can witness it every day."

BBC Moscow correspondent Andrew Harding says there is now overwhelming evidence that Russia's massive air bombardment is causing heavy civilian casualties on a daily basis.

The BBC's Ade Akintonwa: The fiercest assault yet on the Chechen capital

Russia unleashed a new wave of air strikes on Friday, bombing Chechnya's capital Grozny and its second-largest city Gudermes, which troops are trying to seal off.

Russian officials say they are at least half-way towards surrounding the capital Grozny and hope to encircle it completely by the end of the month.

Talks urged

The international community has repeatedly urged Moscow to seek a peaceful solution to the conflict. US President Bill Clinton called on the two sides to "stop fighting and start talking".

But Russia's Prime Minister, Vladimir Putin, said on Friday that the West supported his country's firm stance against terrorism.

The BBC's Richard Lister: "Mrs Albright made crystal clear her concern"

He said he thought Mr Clinton ''was not especially worried about the tough measures taken by Russia against terrorists".

Militants in Chechnya have in the past launched violent raids on neighbouring regions and have been blamed by many for the recent bomb attacks in Moscow and elsewhere.

Chechnya's spokesman in Europe, Salih Brandt, said the war was effectively being financed by the international community.

"It's the IMF money, the British money, the American money, the German money which is propping up the Russian economy.

"And that's all going into the Russian war machine and killing these people."

UN mission

The United Nations has meanwhile announced plans to send a team of humanitarian experts to parts of Russia bordering Chechnya to assess the needs of thousands of people who have fled the fighting.

Kofi Annan: The solution must be political

The team is to leave within days and is expected to go to Ingushetia and Dagestan, where almost 200,000 Chechens have taken refuge.

UN Secretary-General, Kofi Annan, has also sent a senior official to Moscow to discuss sending a UN humanitarian mission to Chechnya.

Mr Annan appealed to both sides to show restraint and take special care to avoid civilian casualties.

"In situations as complex as that in Chechnya, the solution must ultimately be political," a UN spokesman added.

Civilian casualties

BBC UN correspondent Mark Devenport: "Team to be the eyes and ears of the international community in the region"

Chechen President Aslan Maskhadov - in a letter urging Pope John Paul II to use his influence to stop the Russian offensive - said 3,265 civilians had been killed and 5,000 others wounded since Moscow's first air assaults on 5 September.

Reports from Russia on Friday said some 222 federal servicemen had been killed and a further 584 wounded.