The move came as a small column of Russian tanks and armored vehicles left the strategic Georgian city of Gori in the first sign of a Russian pullback of troops from Georgia after a cease-fire intended to end fighting that reignited Cold War tensions. The two countries on Tuesday also exchanged prisoners captured during their brief war.

However, Russian soldiers took Georgian servicemen prisoner in Poti—Georgia's key oil port city—and commandeered the U.S. Humvees.

Russian forces blocked access to the city's naval and commercial ports on Tuesday morning and towed the missile boat Dioskuria, one of the navy's most sophisticated vessels, out of sight of observers. A loud explosion was heard minutes later.