After Russia won control of South Ossetia, officials in Tbilisi raised fears of a new front opening in western Georgia, saying Moscow was preparing to attack another pro-Russian restive Georgian province, Abkhazia.
Russian aircraft bombed the only part of Abkhazia controlled by Georgian forces overnight and attacked a Georgian town near the rebel region, interior ministry officials said.
"We have verified information that the Russians are planning to attack Zugdidi in several hours," Georgian parliament speaker David Bakradze said, referring to a Georgian-controlled city near Abkhazia.
Interior ministry spokesman Shota Utiashvili told AFP that Russia had asked the United Nations to withdraw its observers from territory near the region.
Earlier Sunday, Georgia said it had withdrawn its troops from South Ossetia, where artillery fire from both sides was exchanged overnight, according to South Ossetian separatists.
AFP reporters witnessed Russian attack helicopters hovering over the area and a stream of people fleeing the devastation carrying their belongings.
Georgia also claimed Russian jets had bombed a military airfield near the Georgian capital Tbilisi overnight and that Moscow had brought 10,000 extra troops into the region amid a build up in armoured vehicles.
"We have left practically all of South Ossetia as an expression of goodwill and our willingness to stop military confrontation," Georgian National Security Council Secretary Alexander Lomaia told AFP.
As diplomatic efforts intensified to bring an end to the crisis, Lomaia said Georgia had asked the United States to act as a mediator to end the conflict, which has claimed 2,000 lives according to Russian figures.
"We have asked United States Secretary of State Condoleezza Rice to mediate with the Russians, to transmit them our message," said Lomaia.
The White House responded using strong diplomatic language, warning Russia that its "disproportionate and dangerous escalation" of the conflict could significantly harm relations between Washington and Moscow.
The United States said Sunday that Russia's reaction to any Georgian withdrawal from South Ossetia would be a key test of the country's true intentions in the region.
President George W Bush on Saturday had led a chorus of international calls to end the hostilities which observers fear might spread to other parts of the volatile Caucasus region.
French Foreign Minister Bernard Kouchner and his Finnish counterpart were due in Tbilisi later in the day, the EU's envoy to Georgia said.
Russia backs the separatist government in South Ossetia and sent in tanks and troops on Friday in response to pro-Western Georgia's military offensive to take back the province which broke away in the early 1990s after a separatist war.
In a new move underlining Moscow's giant military advantage, Russian moved warships to the Black Sea on the west coast of Georgia and Interfax news agency said they were preparing a blockade to stop military supplies entering Georgia.
"This is definitely necessary for preventing arms shipments to Georgia by sea," Interfax quoted a naval source as saying. "A sea blockade of Georgia will also help avert an escalation of military activity in Abkhazia."
South Ossetian authorities said in a statement that overnight shelling had killed 20 and wounded 150 people in the South Ossetian capital, Tskhinvali, which Russian forces now control.
Russia also continued bombing raids on Georgian territory outside South Ossetia, hitting a runway of a military airfield near Tbilisi international airport early Sunday, according to Lomaia.
On Saturday, Russian aircraft had staged raids on the Georgian port of Poti and the city of Gori, where inhabitants said scores of people were killed.
Lomaia said Russia had concentrated a large number of armoured vehicles near the border with Georgia at a crossing not linked to South Ossetia.
Georgia's army of less than 25,000 men is confronting a Russian force which can count on more than one million troops – and experts say the conflict cannot last.
A meeting of the UN Security Council on Saturday failed to agree on a call for an immediate ceasefire.
France, which holds the EU presidency, announced that it would organise a meeting of European foreign ministers early next week and an emergency EU summit could be held.
The European Union "strongly states its commitment to the sovereignty and the territorial integrity of Georgia and its internationally recognised borders and urges Russia to respect them," said a statement released by France.
The EU "underscores that the military actions (against Georgia) could affect EU-Russian relations," it added.
The conflict with Russia has claimed 150 Georgian lives, Georgian Foreign Minister Eka Tkeshelashvili said Saturday.
Russian officials have said at least 2,000 people have been killed in South Ossetia.
South Ossetia broke from Georgia in the early 1990s. It has a population of 70,000, many of whom have been granted Russia passports.