Russia escalated its conflict with Georgia today, launching further airstrikes and a naval blockade, despite the offer of a ceasefire by Tiblisi and the withdrawal of its forces from South Ossetia.

As the international community called on Moscow to halt its offensive, a damaging new front opened in the province of Abkhazia, where 4,000 Russian troops were reinforcing rebels committed to breaking away from Georgian rule.

Tbilisi international airport was hit by a Russian air strike 200 metres from the runway. In the same air raid, Russian jets bombed a nearby military airport and construction plant.

The Russian army claims that Georgian forces were still active in South Ossetia, despite receiving a Georgian note declaring an end to military activities.

“There are indications that exchanges of fire are continuing and the Georgian forces have not been fully withdrawn from the conflict zone,” Russian Foreign Ministry sources told Interfax.

President Mikheil Saakashvili of Georgia accused Russia of trying to overthrow his government, but Moscow vowed to continue the fight, saying that Georgian officials could face charges of war crimes for attacking the South Ossetian capital on Thursday.

“They want the whole of Georgia,” Mr Saakashvili said. “The Russians need control over energy routes from central Asia and the Caspian Sea,” he told a German newspaper.

Vladimir Putin, the Russian Prime Minister, hinted today that South Ossetia could be subsumed into Russia, and laid responsibility for the fighting at Nato’s door.

"Georgia's aspiration to join Nato ... is driven by its attempt to drag other nations and peoples into its bloody adventures," he said.

Russia’s expanded offensive included an attempt to blockade Georgia by sea. “It [the blockade] is necessary for preventing arms shipments to Georgia by sea," a naval source told the Interfax news agency.

Georgian officials said that 4,000 Russian troops were expected to land in Abkhazia and there are fears that Russia could strike into Georgian territory from there.

Abkhaz fighters began to attack the Kodori Gorge, a region in Abkhazia that Georgia took back in 2006, and Georgian officials said Russian jets were attacking the area.

Georgians began evacuating residents from the town of Zugudidi located close to the border with Abkhazia. “Police cars are driving round telling the population through loudspeakers to prepare for evacuation,” a resident said.

Zalmay Khalilzad, the US envoy to the United Nations, accused Russian of “targetting civilians” and waging a “campaign of terror”. His Russian counterpart, Vitaly Churkin, said: “This is completely unacceptable, especially from the lips of a representative of a country whose action we are aware of in Iraq, Afghanistan and Serbia.”

A spokesman for Gordon Brown called for a cessation of hostilities: "We are urging an immediate ceasefire to the fighting in South Ossetia and calling for a resumption of direct dialogue between the parties."

But on the ground, despite Georgia's withdrawal, the situation in Tskhinvali remained bleak with hundreds of people stuck in basements and bodies lying unburied in the streets.

“There are lots of Georgian bodies in different parts of the city,” said Irina Gagloeva, a South Ossetian government official.

“There is a whole entrance of a house full of bodies on Geroyev street, there is a body of the dead in all the house and something needs to be done quickly,” one resident said, saying that there were no coffins in the town as they had all burnt in the fighting.

Georgia's withdrawal from South Ossetia comes just three days after it launched airstrikes and missiles on the small town of Tskhinvali, the capital of the breakaway republic, in an attempt to force the region back under its control.

President Dmitry Medvedev said he was ordering the military prosecutor to document crimes against civilians in South Ossetia. Both sides have accused each other of atrocities. None have, as yet, been proven.

Many foreign governments told their nationals to leave Georgia as the crisis deepened, with US citizens ordered to join convoys to neighbouring Armenia. Italy, Poland, Germany, Canada and Britain also told their citizens to seek safety in Armenia.

Russia’s deputy foreign minister Grigory Karasin said more than 2,000 people had been killed in South Ossetia since fighting began on Friday, and 30,000 Ossetians had been made refugees.

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