Ukraine's state power company says it has cut electricity supplies to the parts of the Luhansk region that are controlled by Russia-backed separatists, citing debts.
Vsevolod Kovalchuk, head of the power distributor Ukrenergo, said on Facebook on April 25 that "the power supply to territory in the Luhansk region that is temporarily not controlled [by the government] was completely halted" overnight.
Russia reacted angrily, claiming that the supply cuts were politically motivated and violated a peace deal for conflict-torn eastern Ukraine.
The war between Ukrainian government forces and the Russia-backed separatists, who hold parts of the Luhansk and Donetsk regions, has killed more than 9,900 people since April 2014.
Ukraine also cut gas supplies to separatist-held parts of the Luhansk region in 2015, also citing unpaid debts.
Kyiv has accused the area of accumulating 2.6 billion hryvnyas ($97.67 million) in unpaid electricity charges.
Ukraine imposed a trade blockade on the separatist-held areas in March.
With reporting by Reuters and Interfax