Russia has deployed S-300 anti-aircraft missiles in the breakaway region of Abkhazia in Georgia.
The Georgian government - which refuses to acknowledge Abkhazia's independence - says it is "concerned" by the move.
The BBC reports the announcement followed an unscheduled visit by President Dmitry Medvedev to the region.
Russia recognised Abkhaz independence in 2008 after a war with Georgia over nearby South Ossetia.
Russian forces drove Georgian troops out of South Ossetia and then Abkhazia before a peace deal was signed.