Ukraine’s nuclear ghosts have been stirred up again after a drone armed with a warhead hit the protective outer shell of the plant at Chernobyl, the site of the world’s worst nuclear accident. The strike on Friday did not breach the plant’s inner containment shell and radiation levels did not increase.

A drone armed with a warhead hit the outer shell of Ukraine’s Chernobyl nuclear plant, briefly starting a fire, in an attack Kyiv blamed on Russia.

President Volodymyr Zelensky of Ukraine called the damage “significant” but said there were no signs of radiation leaks. A Kremlin spokesman denied that Russia had carried out the strike.