Georgia accused Russia on Tuesday of organising a series of explosions in recent months which left one person dead, in the latest flaring of tensions between the two foes.
The Georgian interior ministry alleged that a Russian military intelligence officer paid a Georgian citizen to set off blasts close to targets including the US embassy and the central railway station in Tbilisi.
"This was an organised terrorist campaign," interior ministry spokesman Shota Utiashvili told AFP. "It was meant to create a general sense of instability and fear in the country."
Six attacks took place between September and November, Utiashvili said. One woman died in the most recent blast in late November.
The main suspect, Gogita Arkania, was detained on Saturday alongside five alleged accomplices, and more explosive devices were found during the arrests, Utiashvili said.
The arrests come a month after Georgia claimed it had smashed a major Russian-sponsored spy ring operating in the ex-Soviet country, where tensions with Moscow erupted into a brief war in August 2008.