Georgia's president has accused Moscow of serious acts of "sabotage" after gas blasts on Russian pipelines cut off supplies to Georgia and Armenia.
Mikhail Saakashvili told the BBC the near simultaneous attacks close to Georgia's border were pre-planned actions orchestrated by Russia.
An electricity transmission line was also destroyed as Georgia experiences extremely cold weather.
Russia's foreign ministry dismissed Mr Saakashvili's remarks as "hysteria".
Russian prosecutors earlier described the attacks as deliberate criminal acts and said an investigation was under way.
Georgia has no gas reserves and was due to run out of gas on Sunday evening, correspondents say.
Relations between Georgia and Russia have been tense since Mr Saakashvili was swept to power by the so-called "Rose Revolution" in 2003, pledging to lead his nation on a pro-Western course.
The two explosions occurred on the main branch and a reserve branch of the Mozdok-Tbilisi pipeline in the Russian border region of North Ossetia at around 0300 local time (2400 GMT).
The electricity transmission line in Russia's southern region of Karachayevo-Cherkessiya - also near the Georgian border - was brought down by an explosion just hours later.
Speaking to the BBC, Mr Saakashvili said there was now huge pressure on his country's energy system, as it was experiencing its coldest weather in more than 20 years.
He said all gas supplies to Georgia were now cut off as was 25% of the electricity supply.
Mr Saakashvili said the gas pipeline was blown up in "an area fully under Russian control... with a heavy presence of Russian border guards", where there were no local insurgents.
"They happened at the same time, and basically they didn't affect supplies to Russia proper, so we can conclude that it was a very well-organised and very well-co-ordinated act.
"We've received numerous threats by Russian politicians and officials at different levels to punish us for basically for not giving them pipelines," the Georgian president said.
Prime Minister Zurab Noghaideli added that the "political motive was clear".
He told the BBC that Russia was seeking "to make a problem for Georgia in winter, to make the government angry and to create instability".
Neither politician offered any evidence to back their claims.
The Russian foreign ministry described Mr Saakashvili's comments as the product of "hysteria and bacchanalia".
Russia's prosecutor's office earlier said what happened were acts of sabotage and that explosive devices had been found, the BBC's Damian Grammaticas in Moscow reports.
A spokesman for Russia's gas monopoly Gazprom said the company was doing all it could to restore gas supplies.
"We believe this situation should not be politicised," Sergei Kuprianov was quoted as saying by the Russian Interfax news agency.
Reports say it could take several days to restore gas supplies, due to the site's remoteness and poor weather conditions.
Georgia is holding emergency talks aimed at securing supplies from Azerbaijan and Iran, but this could also take several days, said Georgian Deputy Energy Minister Aleko Khetagurov.
Russia also supplies gas through Georgia to Armenia, which in turn sends some electricity back to Georgia.
Gas prices to the two countries were doubled in January to $110 per 1,000 cubic metres, as part of a series of recent price hikes for former Soviet countries.
Armenian President Robert Kocharyan is expected to discuss the gas situation in a meeting with Russian President Vladimir Putin, during a visit to Moscow which starts on Sunday.