Georgia accused Russia of breaking a ceasefire in their six-day-old conflict on Wednesday and President George W. Bush demanded Moscow act to resolve a crisis that has strained relations with the United States.
In the strongest gestures yet of U.S. support for Georgia, Bush said he was sending Secretary of State Condoleezza Rice to the former Soviet republic and dispatching military aircraft with humanitarian supplies.
"Russia must keep its word and act to end this crisis," the U.S. president said.
Moscow strongly denied truce violations, although Bush voiced concern about reports of continuing Russian military actions in Georgia.
In a highly charged atmosphere of claim and counter-claim, Georgian President Mikheil Saakashvili said Russian tanks had stormed the Georgian town of Gori and were advancing on the capital, though a deputy minister later backtracked on this. Moscow said the claims were not true.
"No Russian troops or armour are moving towards Tbilisi," Colonel-General Anatoly Nogovitsyn, deputy head of the General Staff, told Reuters.
Witnesses said Russian troops had set up at least two checkpoints several kilometres from Gori and the Russian side later said it had secured an abandoned Georgian ammunition depot outside the town, famous as the birthplace of Josef Stalin.
Russia's far greater military might has humiliated Georgia, which last Thursday launched an unsuccessful strike to try to retake the pro-Russian breakaway region of South Ossetia, provoking massive retaliation from Moscow.
The fighting in the Caucasus, an important transit route for Caspian oil, has unnerved the United States, NATO and the European Union and rattled investors.
In Brussels, the European Union backed sending peacekeeping monitors to South Ossetia to supervise the French-brokered ceasefire. It also agreed to step up humanitarian aid.
"We are determined to act on the ground," French Foreign Minister Bernard Kouchner said after briefing an emergency meeting on his country's mediation efforts as president of the 27-nation bloc.
A NATO spokeswoman said the United States had requested a meeting of alliance foreign ministers on the Georgia crisis, as divided Western powers groped for a response to Russia's overwhelming show of force against its tiny neighbour.
The United States -- a close ally of Georgia -- and Britain have supported Saakashvili and criticised Moscow heavily for a disproportionate response.
But France, Germany and Italy, which all enjoy closer political ties and strong business links with Russia, have been careful not to take sides, pressing instead for the violence to stop.
Flags flew at half mast as Russia and Georgia mourned their dead.
The United States said it had credible reports of continued violence in South Ossetia and urged Russia to restrain "irregular forces" from attacking civilians.
"We have credible reports of villages being burned, shootings and killings," said Washington's envoy to the region, Matthew Bryza.
Saakashvili, making increasingly heated remarks in a plethora of interviews with English-language international TV channels, accused Russia of "atrocities" in South Ossetia.
"Russian tanks are going through villages inhabited by (the) Georgian population and throwing people out of the houses, pushing people into concentration camps that they are setting up in those villages and separating men and women," he told CBS Morning News.
There was no independent verification.
Georgia's Deputy Interior Minister Ekaterine Zguladze later told a news conference: "I'd like to calm everybody down.
The Russian military is not advancing towards the capital." In and around South Ossetia's capital Tskhinvali, which was devastated during the Georgian attack, occasional small-arms fire resounded but there were no major incidents.
"The situation is purely a post-war one," said South Ossetian spokeswoman Irina Gagloyeva.
"Taking advantage of this lull, we are reburying those killed in the Georgian aggression.
"Many were buried in a hurry just where they were killed - in orchards and kitchen yards.
Yesterday, we recovered 18 decomposing bodies from under the rubble in Tskhinvali. Today we found another four."
Georgia to Lose Rebel Regions?
Analysts said Georgia's failed attempt to seize South Ossetia by force last week made it much less likely that the breakaway territory, along with a second rebel region, Abkhazia, would return to Tbilisi's control in the future.
Russia says 1,600 civilians died when Georgia attacked South Ossetia, though the figure has not been independently verified.
Moscow's General Staff says it lost 74 soldiers in the fighting, with 171 wounded and 19 missing. Tbilisi puts deaths on its side at over 175, with hundreds injured. That figure does not include South Ossetia.
Moscow announced an emergency aid package for South Ossetia, with Finance Minister Alexei Kudrin pledging 10 billion roubles ($414 million) to rebuild the shattered region.
The EU-brokered peace plan would provide the basis for a U.N. Security Council resolution to settle the conflict.
But analysts said Georgia may yet have to make painful concessions, having been routed on the battlefield and forced to concede precious ground in both South Ossetia and Abkhazia.
The current version of the peace plan mentions respect for Georgia's "sovereignty and independence" but had no reference to "territorial integrity" -- possibly allowing for discussion about the future status of the separatist territories.
Abkhazia said on Wednesday that its forces had pushed out Georgian troops and captured the disputed upper reaches of the Kodori Gorge on the region's boundary with Georgia proper.
That was a major blow to Tbilisi, since the gorge was the only significant portion of Abkhaz territory under its control.
The West indicated it would call for a multinational peacekeeping force in South Ossetia and Abkhazia to replace the Russian-Georgian joint force, and a new process to settle disputes that have simmered since both regions broke away from Georgian rule in the early 1990s.
Both Abkhazia and South Ossetia are populated by ethnically distinct groups with their own languages.