Parts of Crimea were hit by power outages late on Sunday and the regional power company blamed them on technical problems in a power line from the Ukrainian mainland to the Black Sea peninsula, which has been wrestled away from Kiev by Moscow.
Local residents said there was no electricity in several cities in Crimea including in some districts of the provincial capital of Simferopol, though the city centre was not affected.
Crimea's power provider Krymenergo said in a statement on its website it introduced partial power cuts after a line operated by Ukraine's national electricity company, Ukrenergo, was hit by a technical fault and went down for repairs.
It said the line stretches from Kakhovka in the Kherson region of Ukraine, neighbouring Crimea to the north, to the village of Ostrovskoye on the peninsula.
It said the fault caused damage to a local power line in Crimea and that the outages were needed to allow repairs and prevent any further damage to the grid.
Ukrenergo was not immediately available for comment and has issued no statement on the matter on its website.
Most of Crimea's electricity - as well as water and food - is supplied from the Ukrainian mainland.
On Wednesday, Kiev threatened local authorities in Crimea that it would take "appropriate measures, including of technical and technological nature" should "provocations" against Ukrainian troops in the region not end.
The new pro-Moscow authorities in Crimea ignored the warning and Russian troops have now seized a large part of Ukrainian military facilities in Crimea after Moscow formally annexed Crimea on March 21.
There was no immediate sign that the power cuts could be deliberate action by Kiev, which, along with the West, does not recognise Russia's annexation of Crimea.