The International Committee of the Red Cross said two of its staff were among those killed when Russian aircraft fired at a five-vehicle convoy marked with the Red Cross emblem at Shami-Yurt, 12 miles west of Grozny. The Chechens say 50 people were killed.
The Russian explanation is that its planes were fired on by men with sub-machine-guns in a convoy, which they then attacked from the air, destroying "two trucks with Islamic extremists".
The border between Chechnya and the neighbouring republic of Ingushetia, to which 174,000 refugees have already fled to escape the Russian bombardment, remains closed.
Tarja Halonen, the Finnish Foreign Minister, visiting Ingushetia as leader of a European Union delegation, said a similar number of refugees were still trapped in Chechnya. She added: "Those seeking to leave the conflict zone should be allowed to do so."
In a hospital close to the Chechen border, injured people gave vivid testimony of indiscriminate Russian air and artillery attack.
Vera Yasenko, a Russian who had taught mathematics in a Chechen village for 23 years, was trapped in the ruins of a house that collapsed on her when it was hit by a shell. Ms Yasenko, her leg badly broken, was freed by her Chechen neighbours. She said: "It was thanks to those guys that my life was saved. They put me in a car and every so often they would push me and ask, `Are you still alive?' These are the same people that are called bandits." She denied that there were Chechen fighters sheltering in her village.
The Russian army said yesterday that it had sealed off Gudermes, the second-biggest Chechen city, and controlled the hills overlooking Grozny, the capital. There is also heavy bombing of roads leading south from Grozny towards the Caucasus mountains.
The Russians are avoiding casualties among their troops by bombarding Chechen settlements heavily. What is not clear is whether it is their intention to displace the Chechen population, more than one-third of whom have been driven from their homes, the UN says. Russian leaders say that, after the bombing of Serbia this year, no Nato country has the right to criticise Russia over the war in Chechnya.
But Sergei Kovalyov, the Russian human rights activist and Duma member, has implied that Russia wants to drive out the civilian population.
He said: "In Chechnya, Russia is using Nato's methods to achieve Milosevic's ends." In Grozny, already under heavy shell fire and without electricity or gas, witnesses say the city has largely run out of food.
Chechen rebels have been in contact with Osama bin Laden, says Russia's FSB intelligence service. The Saudi-born Mr Bin Laden is suspected of organising last year's bombings of US embassies in Africa, and other operations. The FSB says Mr Bin Laden promised to help Chechens secure aid from Afghanistan's ruling Taliban movement.Reuse content