Radiation levels at the shuttered plant in the Kyiv region — site of the world's worst nuclear accident — have not increased, according to the U.N. International Atomic Energy Agency, which said the strike did not breach the plant's inner containment shell.

Ukraine said a Russian drone crashed into the containment structure, starting a fire, but so far radiation levels have stayed constant.

A Russian drone struck the former nuclear power plant at Chernobyl in an attack overnight into Friday, Ukrainian President Volodymyr Zelensky has said.