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

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.

For the first time, a Russian projectile directly struck a structure containing a nuclear reactor. Moscow has increasingly been targeting Ukraine's nuclear infrastructure.