The rotation is in line with a May 1994 ceasefire agreement, as well as a mandate on the peacekeeping operation in the conflict zone between Georgia and its breakaway republic of Abkhazia.
"The Russian military echelon has already crossed the Abkhazian border, everything is on schedule," the official said, adding that the rotation was expected to be completed by December 23.
The ongoing rotation of a total of 500 personnel from the Volga-Urals Military District motorized rifle division is to be held in the Gali district and in the lower part of the Kodori Gorge.
No additional military equipment is due to be transported into the conflict zone.
According to Russian military sources, the peacekeeping brigade currently deployed in the Georgian-Abkhazian conflict zone, for the large part in the Kodori Gorge area, totals about 3,000 personnel.
On December 10, Russia completed the first stage of the planned rotation by sending 600 peacekeepers into the conflict zone.
Abkhazia declared independence from Georgia following a bloody conflict that left hundreds dead in 1991-1992, and the CIS Peacekeeping Forces entered the conflict area in June 1994 under the ceasefire agreement signed in Moscow on May 14, 1994.
More than 100 Russian peacekeepers have been killed in the conflict zone since then.
There have been frequent and mutual accusations of ceasefire violations from both Abkhazia and Georgia, whose President Mikheil Saakashvili has vowed to regain control of the region. Peace talks broke off when Tbilisi sent troops into Kodori Gorge in July last year and established an alternative Abkhaz administration there.