A leak of ammonia at a chemical plant near the eastern Ukrainian city of Sumy affected an area within a radius of more than 5 km, Agence France-Presse and the Associated Press reported, citing a statement from the authorities.
Sumy Oblast Governor Dmytro Zhyvytskyi did not say what caused the ammonia leak.
The Sumykhimprom plant is located on the eastern outskirts of the city with a population of about 263,000 people and in recent weeks has come under fire from Russian troops, according to BTA.
Authorities urged Sumy residents to breathe through gauze soaked in citric acid and seek refuge in basements, shelters and downstairs. Ammonia is lighter than air and rises, Zhyvytskyi said in a statement on the Telegram. He added that the plant has emergency services.
According to the governor, the city of Sumy is not under immediate threat due to the prevailing winds.