Russian President Vladimir Putin has said Georgia's arrest of four Russian army officers for spying was "an act of state terrorism with hostage-taking".
He was speaking after a meeting of his security council to discuss the crisis.
He said Georgia was trying to provoke Moscow with the help of "foreign sponsors" and compared its leadership to that of Soviet leader Josef Stalin.
Correspondents say it is Russia's worst crisis in relations with its neighbour in more than a decade.
In his first public comments on the crisis, Mr Putin likened the arrests to the repression of Soviet dictator Josef Stalin's feared police chief, saying they were "a sign of the political legacy of Lavrenty Pavlovich Beria".
Both Stalin and Beria were Georgian.
"They clearly want to pinch Russia in the most painful way, provoke it," Mr Putin said in televised remarks at the start of a session of the presidential security council.
"These people think that under the roof of their foreign sponsors they can feel comfortable and secure. Is it really so?"
He then denounced the arrests as "an act of state terrorism involving the taking of hostages", the Kremlin said in a statement.
On Friday, four Russian officers who had been detained in Georgia on Wednesday were charged with spying and were ordered to be held for two months pending investigations.
Russia recalled its ambassador to the Georgian capital, Tbilisi, and began a partial evacuation of its staff from the country.
On Saturday, Russia announced it was suspending the withdrawal of its troops from Georgia, which had been expected to be completed by the end of 2008.
Georgian Foreign Minister Gela Bezhuashvili said his country expected Russia to honour the pullout agreement, and accused Moscow of trying to scare the Georgian people.
Georgian President Mikhail Saakashvili has described Moscow's reaction to the arrests as "hysteria".
Russia has urged the United Nations Security Council to take action to restrain Georgia.
Relations between Moscow and Tbilisi have deteriorated in recent weeks, since Georgia and the Western military alliance Nato agreed to hold talks on closer relations, correspondents say.
Georgia has also accused Russia of actively trying to undermine its government by backing separatists in Abkhazia and South Ossetia.
Relations between the two nations had already become increasingly tense since Mr Saakashvili was elected president of Georgia in 2004, pledging to take the Caucasian nation out of Russia's orbit and join Nato and the European Union.