Smoke rises from the scene of the explosion
A blast in Georgia's breakaway region of South Ossetia killed seven Russian soldiers, a Russian commander says.
The soldiers died when a car full of explosives blew up near a Russian military base in the regional capital, Tskhinvali, local officials said.
Georgia said Russia organised the explosion as a pretext to delay withdrawing troops from South Ossetia.
But Russia blamed Georgia, saying it was an attempt to undermine a ceasefire agreement between the two sides.
Tension remains high in the region following the conflict between Russia and Georgia over the summer.
Seven other soldiers were injured in the blast, the Russian military commander in South Ossetia said.
According to a statement from the South Ossetian breakaway government, Russian troops had confiscated the vehicle that blew up from an ethnic Georgian village because it was carrying weapons.
Russian television footage showed a black plume of smoke rising from behind metal gates at the base.
Russia says it plans to keep thousands of troops in South Ossetia
An unidentified Russian foreign ministry official said forces "striving to destabilise the situation" were behind the blast, Russian media reported.
South Ossetian leader Eduard Kokoity went further, describing it as "a deliberate terrorist act prepared by the Georgian Security Ministry", Russia's Itar-Tass news agency said.
Georgian Interior Ministry spokesman Shota Utiashvili rejected the allegation.
"I think this is a provocation with the aim of keeping Russian forces in Georgia," he told the AFP new agency.
The BBC's James Rodgers, in Moscow, says it is the most serious incident in South Ossetia since Russia and Georgia fought over the territory two months ago.
Fighting began there on 7 August when Georgia tried to retake South Ossetia by force after a series of lower-level clashes.
Russia launched a counter-attack and the Georgian troops were ejected from South Ossetia and another region, Abkhazia, several days later.
Earlier this week, European Union monitors entered a Russian-controlled buffer zone around South Ossetia, as part of a French-brokered peace deal between the two sides.
Russia says it will pull out from the buffer zone and another around Abkhazia by 10 October.
But it has recognised the two breakaway regions as independent and says it will keep nearly 8,000 troops in the two areas.
The EU wants its observers to have access to the breakaway regions, but Russia has repeatedly refused to guarantee that.