Ukraine introduced emergency power cuts in six regions amid what authorities described as a "massive" Russian missile strike, the national grid operator said on Wednesday.
Kyiv's air force had warned of numerous groups of missiles launched by Russia amid a nationwide air-raid alert, but there were no immediate reports of damage.
In a statement, Ukrenergo said it had introduced the power cuts in the Kharkiv, Sumy, Poltava, Zaporizhzhia, Dnipropetrovsk and Kirovohrad regions.
Separately, Ukrainian energy minister German Galushchenko said on social media that "preventative measures" involving the distribution system were also in force.
Russia has carried out regular air strikes on Ukraine's energy grid as its ground forces press ahead on the battlefield in the Kremlin's three-year-old invasion.
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