Earlier on Friday, Eduard Kokoity, the South Ossetian separatist leader, told Russia's Interfax news agency that 1,400 South Ossetians had been killed in the fighting.
One hundred and fifty Russian tanks, armoured personnel carriers and other vehicles entered South Ossetia to back the breakaway region against the Georgian army earlier on Friday.
He said: "About 1,400 died. We will check these figures, but the order of the numbers is around this. We have this on the basis of reports from relatives."
The separatist region has been under heavy attack from Georgian forces since a brief ceasefire on Thursday night.
Both sides claim to have the upper hand in the fighting.
The Georgian military says it has "liberated" the area, while some sources say Tskhinvali has been virtually destroyed and Russian troops are on the point of entering the city.
The capital has a population of about 42,000 people.
| The Red Cross said Tskhinvali's main hospital has stopped functioning [Reuters]
Jonah Hull, Al Jazeera's correspondent on the border between Georgia and South Ossetia, said that the Georgians were confident of taking on the Russians due to the considerable training and weapons they had received from Western powers in recent years.
"It look like it will be a turbulent night for the citizens in the city," he said.
The Russian defence ministry says 12 of its peacekeepers have been killed and 150 wounded.
Mikheil Saakashvili, the Georgian president, said 30 soldiers had been killed on the
the Georgian side.
Saakashvili said he was urgently recalling 2,000 troops serving in Iraq, in response to the fighting in South Ossetia.
"One brigade of Georgian forces is in Iraq and we are calling it home tomorrow," he said.
Earlier, the International Committee of the Red Cross (ICRC) said that the main hospital in Tskhinvali had ceased functioning.
Local medical officials told the organisation that the Respublika Hospital closed hours after Georgia launched its military offensive.
Maia Kardova, an ICRC spokeswoman in Tbilisi, the Georgian capital, said the news is "very alarming" because emergency access to South Ossetia has been cut off since fighting began early on Friday.
She said ambulances are unable to reach wounded civilians in the city.
At the headquarters of the ICRC in Geneva, the organisation called for a "humanitarian corridor" to allow the evacuation of those wounded in the fighting.
|Georgian villagers near Tskhinvali leave their houses [Reuters]
Anna Nelson, an ICRC spokeswoman, said: "We are calling for the opening of a humanitarian corridor to enable ambulances to evacuate wounded people and to enable civilians to be evacuated out of the conflict zone.
"We call on sides to respect international humanitarian law and to not target civilians and to ensure that medical facilities and medical transport can treat wounded as necessary."
The neutral, Swiss-based humanitarian organisation voiced concern at the escalation of violence and called for all sides to distinguish between civilians and those taking direct part in the hostilities.
The US and the EU are sending a joint delegation to the region in a bid to seek a ceasefire, a European diplomatic source said.
A US envoy will join a senior official from the French foreign ministry, which currently holds the EU presidency, in an effort to halt the fighting.
The UN Security Council is holding a second emergency meeting in New York on Friday to discuss the situation.