A drone armed with a warhead hit the protective outer shell of Ukraine's Chernobyl nuclear plant early Friday, punching a hole in the structure and briefly starting a fire, in an attack Kyiv blamed on Russia.

A Russian drone attack has hit the radiation shelter protecting Chernobyl's damaged nuclear reactor, Ukrainian President Volodymyr Zelensky has said. The overnight strike at the nuclear plant, which is the site of the world's worst nuclear accident, caused a fire that has since been extinguished, he added.

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