"The investigative group carrying out a preliminary examination has every reason to believe the explosion in Tskhinvali was arranged by Georgian secret services in order to destabilise the situation," a spokesman for the prosecutors investigative department, Vladimir Markin, was quoted by RIA Novosti and Interfax as saying.
Earlier Georgia's interior ministry denied any Georgian involvement in Friday's blast, which took place at a Russian military base in the rebel city of Tskhinvali.
"I think this is a provocation with the aim of keeping Russian forces in Georgia," said Georgian interior ministry spokesman Shota Utiashvili.
On Saturday, Russias Kommersant newspaper predicted the explosion could be used to justify keeping Russian troops in a buffer zone set up by Russia around South Ossetia following an August war between Russia and Georgia that centred on the breakaway region.
Russia troops are due to pull back to positions inside Georgias two rebel regions by October 10 under a European-brokered peace deal that has also seen the European Union deploy over 200 observers to Georgia.
Earlier Russias military confirmed that one of its top officers, Colonel Ivan Petrik, was killed by Fridays blast.