Georgia today said it would never allow the country "to be broken up into pieces" and accused Russian forces of continuing their offensive after Moscow claimed to have stopped the advance.
The Georgian president, Mikhail Saakhashvili, said he would regard Russian troops in the breakaway states of South Ossetia and Abkhazia as occupying forces.
He claimed Russia had been preparing for the crisis in the Caucasus for at least a year, and said its troops and supporters had been deliberately targeting police in an effort to destabilise his country.
US-educated and west-leaning Saakhashvili said Georgia would be leaving the Russia-dominated Commonwealth of Independent States, the organisation representing former Soviet bloc countries.
"Those people who are bombing us want to restore the Soviet Union," he told reporters in Tbilisi, but the people of Georgia did not want to return to the past and would "never surrender".
But Russia denied that its forces were still fighting and said Georgia's claims were provocative.
Meanwhile French president Nicola Sarkozy, visiting Moscow to try to broker a peace deal, said: "We are not at peace yet but we are at a stage of temporary cessation of hostilities, which is certainly significant."
"The night is young," he added, after conceding there is still a lot of work to do.
However, his Russian counterpart Dimtry Medvedev had told him Russia had no intention of staying in Georgia.
Nato also insisted that Russia's halting military action was an important first step, but said Russian and Georgian troops must return to positions they held before fighting started last week.
Georgia said it remained "prepared for everything" until there was more evidence of a halt to operations. Thousands of supporters, holding red and white Georgian flags, packed a rally to hear further defiance from their president.
Before Russia said it had ceased military action, at least five civilians were killed in Gori, which was bombarded by airstrikes, although the Russian general staff denied it was being targeted.
Reports from the scene suggested explosions may have been caused by mortar fire and not by bombs dropped by jets, as witnesses first thought.
The villages of Ruisi and Sakoringo, well outside South Ossetia where the five-day conflict first flared, had also been hit after the supposed cessation of hostilities, according to Tbilisi.
There were also separate reports today of witnesses seeing 135 military vehicles driving through Georgia towards the other separatist province of Abkhazia.
The Georgian prime minister, Lado Gurgenidze, speaking to Reuters news agency, said, "We will need more evidence, everyone in this situation needs a binding agreement. Until that happens, we are mobilised, we are prepared for everything." Despite the Russian gesture he said "there has been more damage to infrastructure and civilian casualties today".
The Russian president, Dmitry Medvedev, who had ordered an end to the fighting, said a full settlement of the conflict could only be reached if Georgian troops returned to their initial positions, were "partly demilitarised", and there was "a binding agreement on the non-use of force".
Earlier, Sarkozy had called for a rapid timetable to be established for each side to go back to positions they held before the crisis. The sovereignty, integrity and security of Georgia must be preserved, he said.
Speaking on national television, Medvedev had said Russian forces had punished Georgia and restored security for Russian peacekeepers and civilians in the separatist South Ossetia region.
"The aggressor has been punished and suffered very significant losses," he said. "Its military has been disorganised."
Soon afterwards, Russian military officials confirmed that forces would remain where they were until there was a reaction from the Georgian government in Tbilisi.
Colonel General Anatoly Nogovitsyn said they would retaliate against any "provocation".
Denis Keefe, the British ambassador to Georgia, told BBC television: "If this news that military operations are stopping is correct, then it is what this country needs and we can then get on to build peace.
"This is a beautiful place with a wonderful people. They don't deserve the suffering that has been inflicted by military operations."
Earlier, Saakashvili said his country had been split in two as Russian forces continued to advance.
He said the main east-west route through Georgia had been cut off, separating the east of the country from its western Black Sea coast.
He accused Moscow of "ethnic cleansing" in the breakaway province of Abkhazia, where local forces were today reported to be trying to remove Georgian troops from the northern area of the Kodori gorge.
The Abkhaz forces' operation was announced by Sergei Shamba, the foreign minister of the Abkhaz separatist government, who said a UN observer mission in the area had been warned and had withdrawn.
"Everything is developing according to plan," he said.
The UN and Nato were also meeting today as the west stepped up efforts to persuade Russia to agree a ceasefire with its US-backed neighbour.
Violence began in South Ossetia, the other Russian-backed separatist province in Georgia, last week.
However, Russian forces have advanced much further into Georgia and are now only a few hours from the capital, Tbilisi.
Moscow has denied it has any intention of marching on the city. Saakhashvili has urged residents not to panic, saying they would have seven or eight hours' warning of any impending troop advance.
The United Nations refugee agency said that nearly 100,000 people had been driven from their homes by the conflict in the Caucasus, Reuters news agency reported.
