Moscow - Seven people were killed and seven injured in a Friday explosion in Georgia's breakaway republic of South Ossetia.

South Ossetian government sources said the blast took place in the capital Tskhinvali, next to a Russian army installation.

All of the victims and injured were Russian service personnel, Russian state-run television reported.

Emergency medical crews and fire trucks responded to the scene. The Russian army base adjacent to the blast is home to a battalion of "peacekeeper" infantry, an elite Russian combat unit.

The powerful blast damaged the Russian infantry staff building and blew out windows in surrounding structures up to a half-kilometre distant.

Mikhael Mindzaev, a South Ossetian police spokesman, said the seventh victim died in hospital as a result of his injuries.

Russia's Itar-Tass news agency reported the bombing seemingly had been aimed at Anatoliy Margiev, a regional administrator appointed by Russian forces.

Margiev's vehicle had just passed the bomb when it went off, said Irina Gagloeva, a South Ossetian spokeswoman.

The bomb was likely detonated remotely by radio command, according to Russian language news reports citing Ossetian police.

The explosion was caused by a bomb concealed in a UAZ four-wheel drive vehicle, witnesses said.

Russian police reportedly had taken the car into custody on their base for detailed investigation, but a bomb inside detonated before law enforcers could find the explosives, the Lenta.ru news agency reported.

Seven people, almost all "peacekeeper" infantry, were seriously injured and transported to hospital, the Russia Today television channel reported.

Eduard Koikoty, South Ossetia's leader, was quick to accuse Georgian special forces of organizing the attack.

The count of injured was expected to rise and it included civilians and Russian military personnel, he said.

The blast took place exactly one week before Russian troops were scheduled to evacuate positions within South Ossetia and Georgia proper.

Koikoty has been outspoken in previous weeks in calls for Russian troops to remain in South Ossetia, despite a ceasefire agreement obliging most of them to leave by October 10.

South Ossetian law enforcers within minutes of the explosion were claiming remains of the car bomb showed the vehicle had been used by Georgian nationals to transport weapons illegally.