Georgia said on Saturday hundreds of Russian soldiers have moved into a disputed Georgian village near breakaway South Ossetia.
Georgian police have reportedly been pushed out, fuelling fears of confrontation.
A regional police official and an interior ministry spokesman said between 500 and 600 Russian soldiers were in the village of Perevi, close to the de facto border with the region.
Russian forces pulled back in October from a buffer zone adjacent to South Ossetia after a five-day war in August, but kept soldiers in Perevi, which sits on the Georgian side of the de facto border.
Russian troops briefly pulled out of the village on Friday, but returned in small numbers by nightfall.
Georgia describes their presence in Perevi as a violation of a ceasefire brokered after the war, when Russia intervened to halt a Georgian military assault on pro-Russian South Ossetia.
South Ossetia claims the village as its own. EU monitors say it clearly lies outside South Ossetia's de facto borders.
Russia has recognised South Ossetia and another breakaway region, Abkhazia, as independent states backed by Russian military protection. The two regions broke away from Georgia in the early 1990s.