A total blackout temporarily hit Crimea after what Russian officials said was an automatic shutoff at a substation providing power to the Russian-controlled Black Sea peninsula.
Shopping centers were dark and trolleybuses stood still in Simferopol, the regional capital, which was entirely without electricity at about 4 p.m. local time on June 13.
Sergei Aksyonov, the head of the Russian-imposed government in the Ukrainian region, said on Facebook that power surges at a substation across the Kerch Strait in Russia had triggered an automatic shutdown of the electricity supply.
"All of Crimea is without power," Aksyonov wrote. He called for calm and said power would be restored within three hours.
Russia's state-controlled power grid company Rosseti later said it had restored the power supply.
Electricity was progressively restored in the peninsula's largest cities within two hours but problems with mobile phone reception persisted, according to an AFP reporter in Simferopol.
Residents reported outages in cities including Yalta and Simferopol, the home of a Russian Black Sea Fleet base.
Russian newspaper Vedomosti cited a resident of another town, Sudak, as saying that there was no electricity there and reporting problems with cell-phone service, and Novaya Gazeta said there were also outages in Yevpatoria.
Authorities in the Russian-held Ukrainian region said that power would be restored within hours.
There was no immediate word on the cause of the outages.
Russia seized control of Crimea in March 2014 after sending in troops, taking over key facilities, and staging a referendum deemed illegitimate by at least 100 countries at the United Nations.
Supplies of electricity to Crimea were curtailed when two high-voltage transmission towers near the isthmus linking the peninsula to the rest of Ukraine were destroyed in November 2015.
Russia laid new transmission cables across the Kerch Strait to Crimea in 2016 but has continued to face problems meeting power needs of the region, which has a population of about 2 million.