Crimea was temporarily without electricity on Wednesday following an incident at a power station in Russia, authorities in the peninsula Moscow annexed from Ukraine in 2014 said.

"The whole of Crimea is without electricity. The power supply will be restored within three hours. Please remain calm," Crimea's pro-Kremlin leader Sergei Aksyonov wrote on Facebook.

He added the blackout was the result of an incident at a power station in Russia's southern Krasnodar region.

"Due to strong voltage surges, the emergency system switched on and disconnected the line," Aksyonov said.

Power was progressively restored in the peninsula's largest cities within two hours but problems with mobile phone reception persisted, according to an AFP journalist in Crimea's capital Simferopol.

Local media Kryminfo cited Maxim Loyko, the director of Crimea's electricity provider Krymenergo, as saying power will be completely restored by the end of the day.

The Russian energy ministry released a statement that almost two and a half million people were left without power in Crimea and in southern Russia.

Crimea was almost wholly dependent on electricity from Ukraine at the time of its annexation by Russia in March 2014, that saw a military operation followed by a referendum not recognised by Kiev and the West.

Ukraine stopped supplying energy to Crimea in late 2015, leaving the region reliant on an underwater cable running from Russia and inhabitants facing frequent problems.

In July 2017, abnormally high temperatures in Russia's Krasnodar region led to electricity cuts that brought Crimea to a standstill, with traffic lights not working and trolleybuses stuck.