Mikhail Saakashvili has said he wants a united Georgia

It was not clear whether they crossed the border with the breakaway region, or reinforced border control points.

Georgian officials say the move is a response to demands from Russian-commanded peacekeepers for the dismantling of Georgian police checkpoints near the region's border.

Georgian President Mikhail Saakashvili has vowed to bring South Ossetia and Abkhazia, back under Georgian control.

Later reports said the troops had been withdrawn again.

The checkpoints were erected about a month ago in ethnic Georgian villages in South Ossetia.

Smuggling row

The authorities in Tbilisi say they are needed to combat a huge problems of smuggling through the border.

But Georgian officials now say the fight against smuggling has irritated Russian peacekeepers and the South Ossetian government, who they claim have stakes in the smuggling business.

South Ossetia broke away from Georgia after a bloody war at the beginning of the 1990s.

It wants to unite with neighbouring Russia and has recently elected a pro-Russian parliament.

But 40% of the population there are ethnic Georgia.