The column, which also apparently included a mobile rocket-launcher, passed the village of Ruisi, outside Gori on the road to South Ossetia Tuesday afternoon.
Col. Igor Konoshenkov, a Russian military officer, told The Associated Press at the scene that the unit was headed for South Ossetia and, ultimately, back to Russia.
Konoshenkov said the movement was part of the Russian pullback mandated by a cease-fire that requires both sides to return to the positions they held before the Aug. 7 outbreak of heavy fighting in South Ossetia, a separatist Georgian province that has close ties to Russia.
Early Tuesday, Russia and Georgia exchanged 20 prisoners of war.
The reported withdrawal was the first sign of the promised Russian troop pullout from Georgia that was supposed to have begun Monday. It came as NATO foreign ministers held an emergency meeting in Brussels to determine a unified response to Russia's invasion of its tiny neighbor.
Also Tuesday, the Organization for Security and Cooperation in Europe said Russia had agreed to allow 20 more international military monitors in and around Georgia's disputed region of South Ossetia.
Finnish Foreign Minister Alexander Stubb said the plan called for the observers to be sent immediately to the Georgian capital of Tbilisi. The organization already has nine observers based in South Ossetia.
Stubb is currently chairman of the OSCE and was speaking on the sidelines of the emergency NATO meeting in the Belgian capital. He said the plan still needed approval from the Georgian government.
Before heading to Brussels, Secretary of State Condoleezza Rice said Monday that Russia was playing a "" with the U.S. and its allies and warned that NATO would not allow Moscow to win in Georgia, destabilize Europe or draw a new Iron Curtain through the continent.
CBS News chief foreign correspondent Lara Logan traveled with Rice to the NATO meeting. The Secretary of State was uncompromising in her rhetoric, which was ratcheted up from her stern but vague words for the Kremlin last week, Logan reports.
"It didn't take the Russian forces long to get into Georgia," Rice said. "It should not take them long to get out."
The goal of Rice and other allies in Brussels is to present a unified message to Russia. "The problem is," Logan said Tuesday, "there are already signs all these different countries are not speaking with one voice."
Some favor a hard-lined approach isolating Russia while others say they don't want to back Russia into a corner - they favor hard-line engagement, but engagement nonetheless.
"When the Secretary of State was asked on her plane yesterday about this issue - what is NATO trying to achieve with this meeting - her answer was that just having this meeting was an achievement," said Logan. "If that's where the bar is, it doesn't seem to be set very high on concrete achievement for us."
The prisoner exchange began as two Russian military helicopters landed in the village of Igoeti, the closest that Russian forces have advanced to the Georgian capital of Tbilisi. Soldiers and men in unmarked clothing got off and two people in stretchers were taken to Georgian officials.
Georgian ambulances later brought two other people to the Russian choppers. One was on a gurney.
Georgian Security Council head Alexander Lomaia told reporters in Igoeti that 15 Georgians and five Russians were exchanged. "It went smoothly," he said. The operation also witnessed by Russian Maj. Gen. Vyacheslav Borisov, who commands troops in the area.
Georgia tried to retake its separatist province of South Ossetia on Aug. 7, launching a heavy artillery barrage. Russian forces immediately came to the aid of their separatist allies, drove Georgian forces out of South Ossetia, and continued their advance until they had a military stranglehold on the country.
The short but intense war stroked tensions between the West and a resurgent Russia.
With Western leaders anxiously watching for a withdrawal and puzzling over how to punish Moscow for what they called a disproportionate reaction to the Georgian offensive, Russian President Dmitry Medvedev defended Russia's actions and warned against any aggression.
"Anyone who tries anything like that will face a crushing response," he said Monday.
Russian troops restricted access Tuesday to Gori, where most shops were shut on Monday and people mobbed a gate where free bread was being handed out. Others milled around the central square, which features a statue of former Soviet dictator and native son Josef Stalin.
Russian troops and tanks have controlled a wide swath of Georgia for days, including the country's main east-west highway where Gori sits. The Russian presence cuts the small Caucasus Mountains nation in half and threatens pro-Western President Mikhail Saakashvili's efforts to keep it from falling apart after the war bolstered the chances that South Ossetia and another Russian-backed separatist region, Abkhazia, will remain free of Georgian rule.
U.S. diplomats denied Russian claims that Washington wants to break up the NATO-Russian Council which was set up in 2002 to improve relations between the former Cold War foes.
But in a reflection of American anger over the Russian invasion, a senior U.S. official said the alliance would rethink a range of planned activities - from a meeting with Russia's defense minister foreseen in October, to regular military consultations in areas like counterterrorism, managing air space or rescue at sea.
The United States had called the emergency meeting of alliance foreign ministers, despite wariness among some European allies about further damaging relations with Moscow.
According to the European Union-brokered peace plan signed by both Medvedev and Saakashvili, both sides are to pull back to positions held before fighting broke out.
But Nogovitsyn said the Russian troops were pulling back to South Ossetia and a security zone defined by a 1999 agreement. Georgian and Russian officials could not immediately clarify the dimensions of the security zone, but Georgian government documents suggest it extends 4.4 miles into Georgia beyond South Ossetia.
French President Nicolas Sarkozy - who brokered the cease-fire deal - has said it allows Russian peacekeepers some patrols until an international mechanism is in place but they cannot be conducted beyond the "immediate proximity of South Ossetia."
U.N. refugee chief Antonio Guterres arrived in Tbilisi for talks with the Georgian government on its relief needs. The agency estimates that 158,000 people have been displaced by the fighting.