Some 2.5m people have been left without electricity in eastern Georgia after an accident damaged two high-voltage power lines, officials have said.
More than 1,000 people were briefly stranded on the underground network in the capital, Tbilisi, when the power outage occurred at 2235 (1835 GMT).
Diesel-powered generators were later used to power the subway trains and allow them to reach nearby stations.
Power outages have plagued Georgia since the collapse of the USSR in 1991.
Residents of the once relatively affluent country are accustomed to blackouts, and many people have their own generators.
Georgia has grown increasingly dependent on hydroelectric power in recent years, as it has been unable to pay for expensive gas and oil imports.
A spokeswoman for the state-run electricity company said damage to two power lines from a hydroelectric power station in western Georgia had been the cause of the blackout.
Nino Dzheranashvili said the accident had been caused by a technical problem.
Georgian authorities said engineers had been deployed to repair the lines and that power supplies would be restored shortly.