Lomaia also said that Russia has moved a large amount of heavy artillery through a tunnel connecting Russia to South Ossetia overnight from Saturday to Sunday.

"Around 100 items of heavy artillery were delivered through the Roki tunnel," he said.

Reports have also emerged that Georgian troops have moved out of their positions in the breakway region of South Ossetia.

Russian tanks and troops surged into South Ossetia late on Thursday to repel a Georgian offensive aimed at reclaiming the region amid fighting that was said to have left hundreds dead.

Temur Yakobashvili, Georgia's reintegration minister, said the Georgian troops left Tskhinvali, the regional capital, to change their location, but remain in South Ossetia.

He said the pullout would help provide a humanitarian corridor to evacuate those injured from the fighting in the city.

Al Jazeera's Jonah Hull, reporting fromg the town of Gori, said that the withdrawal began early this morning.

"There have been eyewitness reports that Georgian troop columns have been moving out of Tskinvali and moving back into Georgian territory," he said.

Russian air raid

"There also appears to be new Georgian defensive positions. "This could be in response to the news that Russia is accumulating arms and artilley on the Russian-Georgian border."

Georgia has said that a Russian planes bombed an aircraft manufacturing plant that houses Su-25 ground jets used by the military in the conflict, located 15km near the centre of Tbilisi.

According to Shota Utiashvili, the Georgian interior ministry spokesman, the attack inflicted some damage to its runways but caused no casualties.

While there has been no offical Russian response to the alleged bombing of the airport, Alan Fisher said injuries had occurred.

"Five people have been injured in what appears to be a Russian air raid," he said reporting from the scene.

"When you speak to people here,  they have no idea why this place would be targeted, while there are military parts housed here, it is not a military base ... some say that perhaps there may have been confusion on the Russian side."

Inside Georgian territory, Russian jets carried out up to five raids targeting military installations around the town of Gori, about 30km outside South Ossetia, on Saturday.

South Ossetia deaths

A spokeswoman for South Ossetia's separatist government said on Sunday that at least 20 people were killed and 150 wounded by Georgian shelling overnight in Tskhinvali, the regional capital.

Fighting in Tskinvali is said to have claimed hundreds of lives [AFP]

Irina Gagloyeva said Georgian forces "fired on Tskhinvali methodically all night. But for now, a relative calm has settled in the city".

"The city is almost fully destroyed. Civilians left in the city are hiding in bomb shelters and basements," she said.

Meanwhile, the United Nations Security Council met for a third time on Saturday to discuss the situation.

Vitaly Churkin, Russia's ambassador to the UN, said a ceasefire "would not be a solution".

"The fighting is still going on. The Georgian forces are continuing to be on the South Ossetian territory," he said.

"The Georgian forces must pull out of South Ossetia.

"And then they must accept the need to sign an agreement on non-use of force with South Ossetians."

Fighting in Abkhazia

There was also fighting in Abkhazia, another breakaway region in western Georgia, where separatist forces say they had launched air and artillery strikes against Georgian troops.

Sergei Shamba, the de facto government's foreign minister, said Abkhazian forces intended to push Georgian troops out of the Kodori Gorge.

The northern part of the gorge is the only area of Abkhazia that has remained under Georgian government control. The region broke away from Tbilisi in the early 1990s  along with South Ossetia.

Georgia's interior ministry on Sunday said that Russian aircraft had bombed a town in the region.

"Russian planes have not stopped bombing the Kodori Gorge since yesterday, and now they are also bombing Zugdidi," a Georgian town  close to Abkhazia, an interior ministry spokesman said. 

On Saturday, Georgian President Mikheil Saakashvili said Georgia had repelled several attacks in the area by Abkhaz separatists.

 The head of Georgia's national security council said Sunday that  Russian naval vessels had arrived in the Abkhaz port of Ochamchira.

Russia has yet to the comment on the claims that it attacked the Kodori Gorge or sent naval vessels to Abkhazia.