A senior security official in Tbilisi dismissed the statement and said by law only Georgian nationals could serve in the country's armed forces.

Asked to list the nationalities of the foreign fighters it believes were involved, Alexander Bastrykin, head of the Prosecutor-General's investigative committee said: "America, the Czech Republic, Chechnya, the Baltic States, Ukraine and Turkey."

"It was a fairly small number of people. They mainly fulfilled support roles," Bastrykin told reporters in Russia's second city of St Petersburg.

He said some had conducted training for the Georgian armed forces. "There were also two snipers ... one from Ukraine and I believe a Latvian woman," he said.

He said he considered the presence of foreign fighters a criminal offence and said he would bring it up at a meeting with representatives of Interpol.

Russia launched a massive counter-offensive on land and sea in August after Georgian forces tried to retake South Ossetia, a Moscow-backed separatist region that rejects Tbilisi's rule.

Western states condemned Russia's actions as disproportionate, but Moscow said it acted to save the lives of innocent civilians and accused the West of fomenting the conflict by arming Georgia.

Responding to Bastrykin's allegation, Kakha Lomaia, the Secretary of Georgia's National Security Council, told Reuters: "It's really difficult to make comments on such absurd statements."

"There are only Georgian citizens in the Georgian army as it's a legal requirement."

"The statement that almost half of the world was fighting in our army in August is just a fantasy of those in the Russian leadership who would like to justify killings of the peaceful population," he said.

(Reporting by Denis Dyomkin in St Petersburg, Russia and Margarita Antidze in Tbilisi; writing by Simon Shuster; editing by Matthew Jones)