The UN cultural agency on Wednesday expressed concern about the suspected poisoning of thousands of schoolgirls across Iran and called for investigations. Thousands of students across hundreds of mostly girls' schools have reported being sickened by toxic fumes in incidents going back to November. There have been no fatalities.

It remains unclear what chemical might have been used, if any. No one has claimed the attacks and authorities have not identified any suspects. Unlike neighbouring Afghanistan, Iran has no history of religious extremists targeting girls' education.