Ukraine said the confinement structure housing a damaged reactor lost power in the incident, and that specialists were currently working to restore electricity.

Ukraine did not elaborate on the consequences of the blackout, and Russia did not immediately comment.

"Due to Russian shelling of energy infrastructure in the Kyiv region, an emergency situation arose at the facilities of Chernobyl Nuclear Power Plant," Ukraine's energy ministry said in a statement on Telegram.

"As a result of power surges, the New Safe Confinement, a key facility that isolates the destroyed fourth power unit of Chernobyl Nuclear Power Plant and prevents the release of radioactive materials into the environment, was left without power," it added.

The New Safe Confinement, completed in 2016, is a large shield-like structure that surrounds the unit four reactor and prevents the release of radioactive material.

A Russian drone attack damaged the confinement structure in February, but did not result in increased radiation in the surrounding area, Ukrainian authorities said.