Prime Minister Denys Shmyhal said on Tuesday Ukraine should prepare for new Russian attacks on its energy infrastructure because Moscow wanted Ukrainians to spend Christmas and New Year in darkness.
He made his remarks after a series of Russian missile and drone strikes which Ukrainian officials say have left electricity supplies in the Kyiv region at a critically low level, with less than half the capital's power needs being met.
"Repairs continue but the situation remains really difficult," Shmyhal told a government meeting.
He said eight nuclear power units and 10 thermal power stations were operating but the energy deficit was "significant."
"Russian terrorists will do everything to leave Ukrainians without electricity for the New Year. It is important for them for Christmas and the New Year to take place in darkness in Ukraine," Shmyhal said.
"That's why we should prepare for new attacks."
Russia, which invaded Ukraine in February, says attacks on basic infrastructure are militarily legitimate. Ukraine says attacks intended to cause civilian misery are a war crime.
Kyiv regional governor Oleksiy Kuleba said 80% of the region was without electricity for a second day after Russian drone attacks on Monday.
"The situation with electricity supplies remains critical," Kuleba said on the Telegram messaging platform. "I want to stress that with every shelling by the enemy, the complexity and duration of the repairs increase."
National power grid operator Ukrenergo said it could provide less than half the required electricity consumption in the capital Kyiv, where winter has set in. The capital's subway system was briefly stopped during the morning rush hour because the electricity supply was unstable.
If electricity is lost, water supplies, heating and mobile phone networks are usually affected. Kyiv mayor Vitali Klitschko said the city had been able to restore water supplies to some consumers.
Shmyhal said the government was planning to triple the number of "invincibility points" where residents can gain access to water, electricity and Internet services. There are currently 5,000 such points.
(Reporting by Olena Harmash and Pavel Polityuk, Editing by Timothy Heritage)