KYIV, Feb 24 - According to Ukrainian authorities, Russian forces have seized the Chornobyl nuclear reactor in northern Ukraine, where the world’s worst nuclear disaster took place in 1986 — and where vast reserves of dangerous nuclear waste remain entombed.

"After a fierce battle, Ukrainian control over the Chornobyl site was lost. The condition of the former Chornobyl nuclear power plant, confinement, and nuclear waste storage facilities is unknown," an official at the plant said on Thursday afternoon, several hours after Russian forces moved across the Belorussian border, towards the plant.