A Reuters reporter saw about 10 Russian military trucks and several armored vehicles leave the main Karaleti checkpoint next to breakaway South Ossetia, heading north towards the de facto border. Russia said the pullback had begun.
Russia has until Friday to pull back troops from buffer zones outside South Ossetia and Abkhazia, another breakaway Georgian region, under a ceasefire deal brokered by France on behalf of the European Union.
The zones were set down after Russia sent in tanks and troops to repel a Georgian offensive to retake pro-Russian South Ossetia.
Russia's counter-offensive against its ex-Soviet neighbor drew condemnation from the West, and deepened fears over the security of the Caucasus as a transit route for oil and gas from the Caspian Sea to western Europe, bypassing Russia.
"Russia has begun the withdrawal of its peacekeepers from all the six checkpoints located in the south of the security zone," Igor Konashenkov, aide to the commander of the Russian military's ground forces, told Reuters.
In western Georgia, a Reuters television reporter saw a column of 50 to 60 Russian military vehicles leave a military base and cross the Inguri river into breakaway Abkhazia.
An unarmed EU observer mission is monitoring the pullback. Chief monitor Hansjoerg Haber told Reuters Russian troops were lifting checkpoints in western Georgia near Abkhazia.
"They are being moved. One or two have been lifted already," Haber said by telephone from the western town of Zugdidi. He said it would be up to the EU in Brussels to confirm Russia's compliance with the ceasefire deal.
Marat Kulakhmetov, commander of Russian peacekeeping forces in the Georgia-South Ossetia conflict zone, said the pullout would be completed in daylight hours. "Everything is completely on track," he told reporters.
A second line of Russian troops is located on the de facto border with South Ossetia.
The five-day war in August followed months of skirmishes between separatists and Georgian troops.
Pro-Western President Mikheil Saakashvili, who has angered Russia by setting Tbilisi's sights on NATO membership, sent in the army to retake South Ossetia more than 15 years after it threw off Georgian rule.
Russian troops drove the Georgian army out of South Ossetia, and pushed further into Georgia, saying they needed to prevent further Georgian attacks.
The West has condemned Russia for a "disproportionate response" to Georgia's actions and has repeatedly demanded that Moscow pull its troops out of core Georgia.
The Kremlin has since recognized both rebel regions as independent states, and plans to station 7,600 soldiers there.
Georgian police are expected to move into the zones behind the retreating Russian troops, to avoid a security vacuum the EU monitors fear could be exploited by paramilitaries. Thousands of Georgian villagers fled the South Ossetia buffer zone, and rights groups say militias were looting and burning homes.