Russia has had S-300 anti-aircraft missiles deployed in Abkhazia since its forces briefly invaded Georgia two years ago to protect two breakaway Georgian regions, a Kremlin source confirmed Friday.

"All of our partners were informed," the Kremlin official told the Interfax news agency.

Russia's air force Commander-in-Chief General Alexander Zelin revealed on Wednesday that S-300 missiles, one of the world's most powerful anti-aircraft weapon systems, had been deployed to protect the airspace over Abkhazia and South Ossetia as well as southern Russia.

He did not specify when the missiles had been deployed to Abkhazia.

Russian forces poured into Georgia in August 2008 after fighting broke out over South Ossetia, and following an EU-brokered ceasefire, recognised both territories which it had long supported as independent.

Georgia immediately condemned the deployment of the missiles as upsetting the balance of forces in the region, and the European Union said their deployment violated the ceasefire agreement.

The United States said however it believed their presence in the region was not new.

"I believe it's our understanding that Russia has had S-300 missiles in Abkhazia for the past two years," State Department spokesman Philip Crowley told reporters in Washington on Wednesday.

First manufactured by the Soviet Union in 1978, the S-300 is a surface-to-air missile system capable of tracking and destroying ballistic missiles, cruise missiles, and low-flying aircraft at a range of up to 100-200 kilometres (62-124 miles).