Russian President Vladimir Putin on Wednesday made a surprise visit to Crimea, inaugurating an undersea cable project to bring a new power supply to the strategic Black Sea peninsula.

Russian President Vladimir Putin on Wednesday made a surprise visit to Crimea, inaugurating an undersea cable project to bring a new power supply to the strategic Black Sea peninsula.

Until late November, Crimea's electricity had mostly been supplied by Ukraine. But the territory's population of nearly two million has been plagued by power cuts since Crimea's four main pylons in Ukraine were blown up late last month.

Russia annexed Crimea in 2014 from Ukraine after a nation referendum.

Putin on Wednesday "went to Simferopol where he inaugurated the first phase of the energy bridge that will provide Crimea's power supply from Russia", Crimea's pro-Moscow deputy prime minister Ruslan Balbek said.

"The first electricity line should have been operational on December 20 but the works have been speeded up... It is a historic day for Crimea, which has won its energy independence from Ukraine," he added.

The electricity cables linking Russia to Crimea are now expected to be up and running on December 15, Balbek said.

Putin meanwhile warned residents of Crimea that "there may still be some problems", according to Russian news agencies.

"I hope the second phase will be launched soon," he said.

"The work is far from done but I am convinced that everything will be done on time."

No one has claimed formal responsibility for the blasts that led to the Crimean power outage.

Authorities in Crimea have blamed the Ukrainian government, though Kiev has insisted it did not know who was behind the explosions.