Some 70% of Tajikistan was left without electricity on Monday as the country's Nurek-Regar hydropower plant shut down, a power holding spokesman said, RIA Novosti reported.
The shutdown occurred at 6:30 local time (01:30 GMT), Barki Tochik's spokesman Nozir Yodgori said.
He said the blackout followed the country's withdrawal from the Unified Power System of Central Asia several days ago.
Dushanbe, the capital of the former Soviet republic, has also been left without power.
"The failure at power transmission lines run by the republic's hydropower plants has caused no danger," Yodgori added.
He also pledged power supplies would be resumed within the next few hours.