They were declared hours after Vladimir Putin vowed to continue hitting Ukraine’s energy infrastructure.
The Kremlin launched its latest attacks on Monday, timed to hit millions as winter temperatures plummet – and just as emergency blackouts were due to end.
Ukrainian grid operator Ukrenergo said: “Because of damage caused by missile strikes to power plants and the high-voltage network, the system has a significant shortage of electricity.”
The situation has been made worse by severe frost, rain, snow and strong winds, which are causing wires to ice over in western regions.
But the east, where fighting has been fiercest, is suffering most. Zaporizhzhia governor Oleksandr Starukh said: “There is a lack of energy – up to a third of what is needed.”
The country’s largest private power producer, DTEK, said blackouts were launched in and around the capital Kyiv, the southern region of Odesa and central Dnipro. Russia, which invaded Ukraine in February, says strikes on vital infrastructure are militarily legitimate.
Kyiv says the grid attacks are a war crime and “amount to genocide”.