Several explosions could be heard in Kyiv as officials reported high-voltage facilities across Ukraine being hit by Russian missile attacks on Friday morning.
Ukraine's power grid operator Ukrenergo said that several facilities in eastern, southern and western Ukraine had been hit, causing disruption to power supply.
Reuters journalists heard at least three explosions in Ukraine's capital city, Kyiv.
The mayor of eastern Ukraine's largest city, Kharkiv, confirmed an infrastructure facility there had been hit and warned of possible power outages as a result.
Ukrenergo said Russia attacked Ukraine's grid overnight with drones and missiles, targeting power stations and transmission facilities.
Moscow, which launched an invasion of Ukraine nearly a year ago, has waged a campaign of massed missile strikes targeting Ukraine's critical infrastructure since last October.