"There is no sign that anything has been stepped up as far as security is concerned ... [but] people are obviously nervous and concerned after the three loud explosions were reportedly heard," he said.
As the United Nations security council met for a third time 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."
Many of the council members, who met in private chambers, appealed for an immediate ceasefire and "expressed grave concern on the further deterioration of the situation," Jan Grauls, Belgian ambassador and the council president this month, said.
"And it is clear that the conflict has now expanded to other areas of Georgia than only South Ossetia."
However, the 15-member council, on which Russia has a veto, was unable to reach an agreement as the United States pushed for a deal that respected Georgia's sovereignty, diplomats said.
Georgia 'under attack'
Russian jets carried out up to five raids targeting military installations around the Georgian town of Gori, about 30km outside South Ossetia, on Saturday.
"Nobody here suspected it [Gori] would come under attack," Al Jazeera's Jonah Hull, reporting from inside Gori, said.
|An apartment building in Gori was hit [EPA]
"Civilians were hit very hard by these attacks, allegedly targeting military facilities but not doing a very good job of it.
"Russia says it is bombing Georgia into peace," he said.
The Reuters news agency reported that at least one bomb hit an apartment block, killing five people.
Georgia has said that a Russian air raid "devastated" the Black Sea port of Poti.
Mikhail Saakashvili, Georgia's president, called the attacks an "unprovoked brutal Russian invasion".
"This is about annihilation of a democracy on their borders," he told the BBC news organisation.
"We on our own cannot fight with Russia. We want immediate ceasefire, immediate cessation of hostilities, separation of Russia and Georgia and international mediation."
There was also fighting in Abkhazia, another breakaway Georgian region,
where separatist forces had launched air and artillery strikes against Georgian troops, according to the de facto government's foreign minister.
Sergei Shamba 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.
A spokesman for the pro-Georgian Abkhaz government-in-exile said the bombings had been carried out by Russian warplanes.
"Earlier today ... Russian jet fighters bombed two villages in the upper part of the gorge," Raul Kiria, the government in exile's spokesman, said.
Edmond Mulet, assistant secretary-general for peacekeeping operations, said the UN was immediately pulling out the military observers in Kodori on advice from officials in Abkhazia.
"At this point we are particularly concerned that the conflict appears to be spreading beyond South Ossetia into Abkhazia," Mulet said on Saturday, adding that Abkhazia had warned of preparations for "a military operation in the Upper Kodori Valley, probably tomorrow morning".
Tskinvali 'in ruins'
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.
|Russia sent more troops and tanks into South Ossetia on Saturday [AFP]
Dmitry Rogozin, Russia's ambassador to Nato, said "98 per cent of Tskhinvali" was in ruins. "Our troops have re-established control over the city," he said.
However, Eka Sguladze, Georgia's deputy interior minister, said Georgian forces had knocked out about 40 Russian tanks around Tskhinvali and "thwarted a Russian tank attack".
A South Ossetain government statement said that firing died down in the capital early on Sunday and that 12 Georgian tanks were destroyed on the city's outskirts.
Russia's Vitaly Churkin told the UN security council that 2,000 people had been killed in South Ossetia, out of a population of about 70,000.
Tskhinvali residents who survived the bombardment and later escaped the city estimated that hundreds of civilians had died. They said bodies were lying everywhere.
Vladimir Putin, Russia's prime minister, travelled to the Russian city of Vladikavkaz on Saturday where he met some of the 34,000 people who had fled the fighting.
"The actions of the Georgian powers in South Ossetia are, of course, a crime - first of all against their own people," Putin said.
"The territorial integrity of Georgia has suffered a fatal blow."
Russia is the main backer of the South Ossetian separatists and the majority of the region's population, who are ethnically distinct from Georgians, have been given Russian passports.
"Russia is saying that it is actually responding to a direct attack on its citizens and on its 'peace keepers' in South Ossetia," Alexander Nekrassov, a London-based Russian analyst, told Al Jazeera.
"This is a difficult legal situation here because techinically speaking South Ossetia is in the territory of Georgia, so any big Russian troop movement can be interpreted as an invasion of Georgia."