Alexander Glukhov was captured by Georgian armed forces in the Akhalgori region of South Ossetia and taken to Tbilisi [Georgia's capital]," a defence ministry spokesman was quoted as saying by Russian news agencies.
The Akhalgori district was seized by Russian forces during the brief war in August between Russia and Georgia over South Ossetia.
While part of South Ossetia's former Soviet borders, Akhalgori was under Tbilisi's control after the region broke away from Georgia in the early 1990s.
Georgian Interior Ministry spokesman Shota Utiashvili said the Russian withdrawal was a positive move, but he added that Georgia wouldn't consider it complete until the troops leave the town of Akhalgori, near South Ossetia, and the Kodori Gorge in another Moscow-backed breakaway province, Abkhazia.
Russia maintains that Akhalgori is part of South Ossetia and considers the Kodori Gorge part of Abkhazia - claims that Georgia rejects.
Georgia has also called for Russia to withdraw from the Akhalgori
district in South Ossetia and the Kodori Gorge in Georgia's other separatist region, Abkhazia.
Mikhail Saakashvili, the Georgian president, and Lech Kaczynski, his Polish counterpart, "were visiting the checkpoint near Akhalgori when the Russians started shooting", Nato Partskhaladze said on Sunday.
However, in a couple of places they maintained checkpoints and this was where this alleged incident was supposed to have taken place - called Akhalgori - a very tense area that used to be controlled by Georgia, but is now under the control of South Ossetian militias behind the Russian checkpoint.
But Tbilisi had accused Russia of not respecting the ceasefire by keeping forces in Perevi and in the disputed Akhalgori district.
Russian forces remain in at least two positions they did not hold prior to the conflict - the Akhalgori
district of South Ossetia and the Kodori Gorge in Abkhazia.