Ukraine expects to require increased electricity imports during continuing cold weather, the energy ministry said on Thursday after an unexpected outage of one of the Khmelnytskyi nuclear power plant's two reactors.

The ministry said the Khmelnytskyi unit was shut down on Wednesday "for technical reasons" and that investigative work was under way.

Ukraine is likely to increase electricity imports to 4,066 megawatt hours (MWh) on Thursday, up from 3,112 МWh on Wednesday and 1,691 МWh on Tuesday, the ministry said.

Ukraine started exporting electricity shortly before it was invaded by Russia in 2022 but paused sales when Russian forces attacked power infrastructure and seized control of its Zaporizhzhia nuclear power plant.

Exports to Eastern Europe resumed in February, a major boost to Ukraine's beleaguered economy, but it still has to import some power during peak consumption hours.

The energy ministry last week said that Ukraine had reduced the capacity of its nuclear power plants and intended to start a repair campaign ahead of schedule thanks to a period of warm weather and low electricity consumption.

Ukraine has three nuclear power plants that together produce more than half of its electricity. The Zaporizhzhia plant has not produced power since being occupied by Russian forces. (Reporting by Pavel Polityuk Editing by David Goodman)