The Georgian government says separatist forces in South Ossetia are being backed by Cossack fighters from Russia.
Georgia claims South Ossetian troops fired first
Fighting between Georgian and South Ossetian troops has continued despite a ceasefire on Friday, with two Georgian soldiers reported dead on Wednesday.
Georgian Foreign Minister Salome Zourabichvili said the South Ossetian authorities could not control the Cossacks who had gone to help them.
Meanwhile, Russia has rejected calls for wider international intervention.
Georgian President Mikhail Saakashvili had said the international community should take an active role in talks.
He called on world leaders to hold a conference on the future of South Ossetia and send Western peacekeepers to the region, which broke away from Georgia in 1992 following an 18-month conflict.
Russian peacekeepers are already in South Ossetia, but Tbilisi accuses them of siding with the South Ossetians, many of whom want to join Russia.
The Russian foreign minister, Sergey Lavrov, said a peacekeeping force and a joint control commission were already in place to resolve the conflict and further international intervention was not necessary.
In an interview with the BBC, Ms Zourabichvili said Georgia's aim was not
to bring South Ossetia "back under control", but to "reunite the country".
"It's very difficult for a democratic country, a fragile and new democratic country, that is developing its economy to have on its border corrupted regions that are lawless and escape all types of control and where all types of trafficking are happening."
Population: About 70,000
Major languages: Ossetian, Georgian, Russian
Major religion: Orthodox Christianity
Currency: Russian rouble, Georgian lari
She said Russian and South Ossetian media had reported military preparations by the Cossacks in South Ossetia.
She described the Cossacks as a third force operating in the region, and said they had been violating the ceasefire
The BBC's Sarah Rainsford, who has visited the South Ossetian military positions could not confirm the presence of Cossacks.
Russian negotiators have also suggested there is an unnamed third group in the conflict zone.
Russian representative Lev Mironov said: "They need to be captured by joint efforts and be put behind bars or destroyed."
But the South Ossetians have said this unnamed force was made up of
Georgian troops, according to AFP.
"There is a third side that wants war and we must neutralize them together with Russian peacekeepers," said South Ossetian representative Boris Chochiyev.
The fighting has intensified, despite the signing of a ceasefire agreement last Friday.
Georgia claims the first shots in the latest attack were fired on its positions from the South Ossetian village of Sarabuk, killing two Georgian soldiers.
A spokeswoman for the South Ossetian administration told the BBC that Georgian troops opened fire first, adding that no Ossetians were injured or killed.
Officials from all sides were due to meet in the South Ossetian capital, Tskhinvali, on Wednesday, as part of continuing efforts to reinforce the peace, but there appear to be few fresh initiatives on the table.
The BBC's Sarah Rainsford says one issue they will discuss is a demand from Georgia for face-to-face crisis talks between Georgian Prime Minister Zurab Zhvania and South Ossetian President, Eduard Kokoiti.
She says it is still not clear if South Ossetians are ready to meet that request.