Photos of the incident showed a large pink cloud over apartment buildings.
Russian forces struck a tank containing nitric acid at a chemical plant in Ukraine's eastern city of Severodonetsk that they are trying to seize, the local governor said Tuesday, calling on people to stay in shelters.
An air strike by Moscow forces "hit a tank with nitric acid at a chemical plant", the governor of the Lugansk region, Sergiy Gaiday, said on Telegram. "Nitric acid is dangerous if inhaled, swallowed and in contact with skin," he added.
"Do not come out of shelters!" Gaiday said.
He asked remaining residents in the city -- which has seen fierce battles for days -- to "prepare protective face masks impregnated with soda solution".
Pro-Moscow separatist authorities said the tank had "exploded" on territory controlled by Ukrainian forces.
"At the Azot chemical plant, a container with chemicals was blown up. Preliminarily, it is nitric acid," Rodion Mironchik, a representative of the self-proclaimed Lugansk People's Republic, said on Telegram.
He said the territory of the plant was under Ukrainian control.
Ukrainian officials said Tuesday that advancing Moscow forces now control half of Severodonetsk, a key goal for the Russian army.
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