The World Health Organization warned on Tuesday that the “black rain” and toxic compounds in the air in Iran after strikes on oil facilities could cause respiratory problems, and it backed Iran’s advisory urging people ‌to remain indoors.

The UN health agency, which has an office in Iran and works with authorities on health emergencies, said it has received multiple reports of oil-laden rain this week.

Tehran was choked in black smoke on Monday after an oil refinery was hit, in an escalation in strikes on Iran’s domestic energy supplies as part of the US-Israeli campaign.

“The black rain and the acidic rain coming with it is indeed a danger for the ⁠population, respiratory mainly,” WHO spokesman Christian Lindmeier told a press briefing in Geneva, adding that Iran had advised people to ‌stay indoors.

Asked whether the WHO backed that advice, he said: “Given what is at risk right now, the oil storage facilities, the refineries that have been struck, triggering fires, ‌bringing serious air quality concerns, that is definitely a good idea.”

He said the strikes had caused “the massive ⁠release of toxic hydrocarbons, sulphur ⁠oxides and nitrogen compounds, into the air”.