Georgia said Tuesday it was alarmed by reports that volunteers from Russia had started arriving in South Ossetia obviously in preparation for military action, RIA Novosti reported.
The Cossack community in North Ossetia, the Russian republic neighboring South Ossetia, said that several hundred volunteers were ready to protect the unrecognized republic, where at least six people were killed and more than 15 injured in shelling attacks by Georgian troops over the weekend.
Unconfirmed reports later said volunteers had started arriving in South Ossetia. But North Ossetia's interior ministry said Tuesday armed groups would not be allowed to cross the border with the breakaway region.
"We are extremely concerned about Tskhinvali's obvious preparations for war," Georgia's Foreign Ministry said in a statement. "The regime said 300 terrorists, who are Russian nationals, had arrived in the region."
The ministry said Georgia would continue to seek dialogue with South Ossetia and responsibility for any escalation in the violence in the region would rest with Russia.
Tbilisi and Moscow have been locked in a feud over Georgia's two breakaway regions and the ex-Soviet Caucasus state's drive to join NATO.
Tbilisi earlier said the shelling of South Ossetia's capital, Tskhinvali, and a neighboring village had been provoked by the rebel region.
South Ossetia's leader said Monday at least 300 North Ossetians had already arrived in the breakaway region, with up to 2,000 expected. Eduard Kokoity also said other North Caucasus republics had pledged assistance if war breaks out with Georgia.
South Ossetia and Abkhazia broke away from Georgia following the collapse of the Soviet Union in 1991, gaining de facto independence after bloody conflicts with Tbilisi.