Georgia has denounced Moscow's announcement as unacceptable and "provocative".
"This is not acceptable to us ... They cannot increase the number any further," Shota Utiashvili, a spokesman for Georgia's interior ministry, said.
"There has been no increase in forces from the Georgian side, nothing at all. The Russian statement is simply not true."Military 'build-up'
Russia's defence ministry said in a statement on Tuesday that Georgia had amassed 1,500 soldiers and police in the upper Kodori Gorge, a pocket of breakaway Abkhazia which is controlled by Tbilisi.
"Any attempt by the Georgian side to resolve the conflicts with force against Russian peacekeepers and also against Russian citizens ... will be met with an adequate and tough answer," the ministry said.
Although Moscow did not detail how many additional troops would be sent to the provinces, it said that 15 new observation posts would be set up on the front line in Abkhazia.
Javier Solana, the European Union foreign affairs chief, said that Moscow's decision was unwise.
"Even if the increase in peacekeepers is within limits - if we want to diminish the perception of tensions, I don't think it is a wise measure to increase now," he said.Close ties
Moscow has established increasingly close ties with the separatists, including encouraging residents there to take up Russian citizenship and frequently inviting the regions' leaders to Moscow.
|"There has been no increase in forces from the Georgian side, nothing at all. The Russian statement is simply not true"|
Shota Utiashvili, Georgian interior ministry spokesman
Georgia accuses Moscow of attempting to annex Abkhazia and South Ossetia.
Many analysts say that increasing bitter row is part of a dispute between Russia and Georgia over the former Soviet state's attempts to join the Nato military alliance.
A Black Sea enclave bordering Russia, Abkhazia was once the favourite holiday destination of the former Soviet Union's ruling elite.
Like fellow rebel republic South Ossetia, it refuses to recognise Georgian central rule and fought a war in the early 1990s to establish de facto independence.
The 1992-1993 conflict killed 10,000 people and displaced 250,000 civilians before Georgian troops were forced out.