An explosion on Crimea's main electricity line from Ukraine has left parts of the peninsula annexed by Russia in the dark, authorities said Thursday, weeks after power lines were sabotaged by anti-Russian activists.

The only functional high-voltage wires providing electricity to Crimea was damaged after a nearby pylon fell following an explosion of an unknown cause, the Ukrainian police said.

The three other power lines supplying the peninsula had been damaged by explosions in November and left Crimeans without electricity for several days.

Crimean Prime Minister Sergey Aksyonov denounced the incident as a "terrorist attack" and assured that New Year celebrations would not be disrupted, Russian news agencies reported.

Russia's energy ministry said Thursday that more than one million residents of the peninsula of 1.9 million had been affected by power cuts.

Electricity was sporadic in different parts of the peninsula, according to AFP reporters in Crimea.

In Sevastopol -- home to Russia's Black Sea fleet -- authorities on Thursday were forced to cut electricity every three hours to save power.

Annexed by Moscow in March 2014, Crimea still heavily depends on Ukraine for its electricity and water supplies.

Russia announced in early December the launch of an undersea power cable that could reduce the peninsula's dependence on Ukraine, but the line almost immediately overheated and plunged Crimea into darkness.