Iran’s supreme leader said on Monday that if a series of suspected poisonings at girls’ schools is proven to be deliberate, the culprits should be sentenced to death for committing an “unforgivable crime”. It was the first time Supreme Leader Ayatollah Ali Khamenei, who has the final say on all matters of state, has spoken publicly about the suspected poisonings, which began late last year and have sickened hundreds of children.

Iranian officials only acknowledged them in recent weeks and have provided no details on who may be behind the attacks or what chemicals — if any — have been used. Iran has no history of religious extremists targeting women’s education. “If the poisoning of students is proven, those behind this crime should be sentenced to capital punishment and there will be no amnesty for them,” Khamenei said, according to the state-run IRNA news agency.