The BBC reports:
Russian troops have begun handing over control of the area around the town of Gori to Georgian security forces.
A top Russian general refused to say when troops would withdraw - they would remain for days to remove weaponry and help restore law and order in Gori.
A BBC correspondent said a series of explosions was heard coming from hills around the town on Thursday.
Georgia attacked the rebel region of South Ossetia from Gori a week ago, prompting Russian retaliation.
In Moscow, Russian President Dmitry Medvedev met the leaders of South Ossetia and Abkhazia - Georgia's other separatist region - and pledged to support any decision the regions made about their borders.
"Not only do we support it but we will guarantee them both in the Caucasus and throughout the world," Mr Medvedev said.
The Georgian parliament voted unanimously on Thursday to withdraw Georgia from a Russia-dominated regional bloc, the Commonwealth of Independent States (CIS).
Meanwhile, the US has reiterated its support for Georgia, sending the first shipments of humanitarian aid into the country. A US envoy to the region said the initial consignment of bedding and other vital supplies was the first of many that would be arriving by sea and air.
Russia has expressed concern about whether the US is delivering only humanitarian aid.
US Secretary of State Condoleezza Rice is in France for talks with French and current EU President Nicolas Sarkozy. She is expected to go on to Tbilisi on Friday, to express US backing for Georgia's government.
No pull-out timetable
Russian troops occupied Gori after pushing Georgian forces out of South Ossetia, leading to a mass retreat from the city by Georgian troops and civilians.
Gori has also come under air attack, with reports of Russian planes bombing the town after Moscow declared an end to its military operation on Tuesday.
Gori, which lies some 15km (10 miles) from the South Ossetian border and is a key link to the Georgian capital, Tbilisi, had been reported calm earlier on Thursday.
The BBC's Gabriel Gatehouse, in the town, said local residents reported feeling safe and secure on Wednesday night, with Russian troops clearly in charge of the town.
But the situation appeared to change on Thursday as a series of blasts were heard around Gori. Journalists, including the BBC's correspondent, were forced to leave their positions quickly.
Russia's continued deployment of troops in Gori has raised concerns that the Kremlin will not make a quick withdrawal from Georgian territory, despite agreeing to a European peace plan.
General Anatoly Nogovitsyn, deputy chief of staff of Russia's armed forces, told a news conference that Russian forces in the region were not ready to withdraw yet.
He said they were protecting abandoned weapons and ammunition, preventing looting and clearing mines left by Georgian forces. They were also liaising with local Georgian authorities and would ensure the security of humanitarian operations, he said.
Elsewhere, eyewitnesses in the Georgian Black Sea port of Poti said that Russian troops had entered the town in armoured vehicles.
Moscow had earlier denied the reports but Gen Nogovitsyn said it was legitimate for Russian peacekeepers to be in Poti as part of intelligence-gathering operations.
He also said Russia was worried "as a matter of principle" about what supplies were being delivered by the US to Tbilisi airport.
Meanwhile, Reuters reports that more than 100 Russian vehicles, some of them armoured, have gathered outside the major western Georgian town of Zugdidi.
Nato debate rekindled
The Georgian government says that 175 people, mainly civilians, were killed during the conflict with Russia and South Ossetian separatist forces.
Russia, which says that 74 of its troops were killed, reports that more than 2,000 people died in South Ossetia, the vast majority civilians allegedly killed in the Georgian attack.
While none of the casualty figures have been verified independently, the UN refugee agency estimates that some 100,000 people have been displaced by the fighting, both from South Ossetia and Georgia proper.
Both sides have accused each other of committing atrocities during the conflict, although little conclusive evidence has been found.
The US special envoy to the region, Matthew Bryza, told the BBC that the outbreak of violence in the Caucasus strengthened Georgia's case to join the Nato alliance.
"Russia, a country with 30 times the population [of Georgia] decided to roll into its much smaller neighbour and tried to roll over it. It failed to roll over Georgia, but it would never have even thought of doing this if Georgia were already a member of Nato," he said.