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 struck the former nuclear power plant at Chernobyl in an attack overnight into Friday, Ukrainian President Volodymyr Zelensky has said. The strike hit the concrete shelter that covers the plant’s destroyed former fourth power unit,

The outer shell that was struck is a protective cover built in 2016 over a heavy concrete containment structure. Soon after the 1986 disaster, the inner layer (in which there was no indication of a breach on Friday morning), was placed on the plant’s fourth reactor. The containment shells seek to prevent radiation leaks.