The supreme leader of Iran on Monday said the poisoning of Iranian schoolgirls in recent months was an "unforgivable" crime after a spate of incidents that have left hundreds of students hospitalized.

State media and officials say more than a thousand girls in different schools across the country have suffered "mild poison" attacks since November.

New spate of poisonings

The Iranian leader's comments came after more Iranian schoolgirls were hospitalized on Saturday, as concerns grow over cases at girls' schools across the country.

The Iranian semi-official Tasnim news agency and Mehr news agency reported that girls at schools in western Hamedan province and northwestern Zanjan and Azerbaijan provinces fell ill on Saturday.

The news agencies said schools in the southwestern province of Fars and the northern province of Alborz reported possible cases of poisoning as well.

"Authorities should seriously pursue the issue of students' poisoning. This is an unforgivable crime... the perpetrators of this crime should be severely punished," state media quoted Ayatollah Ali Khamenei as saying.

"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 was reported as saying.

More than 30 schools across at least ten provinces reported girls falling mysteriously ill, though the number of schools reporting suspected poisoning cases differs from outlet to outlet. Iran has 31 provinces.

Parents take to the streets

The news reports said that dozens of students had been transferred to local hospitals for treatment and that students were in generally good condition.

Unverified social media footage clips also showed parents taking children home from schools and ambulances taking students to hospitals.

Parents took to the streets in the Iranian capital of Tehran to protest against the suspected poisoning attack on Saturday too.

In Iran, girls account for more than 50% of students enrolled in schools.

Iranian President Ebrahim Raisi has asked ministers to follow up on the cases, dubbing them "the enemy's conspiracy to create fear and despair in the people."

What do we know about the latest wave of sickness?

Iran's Interior Minister Abdolreza Rahmani Fazli said on Saturday investigators had found "suspicious samples" that were being studied.

In a statement carried by Iran's official IRNA news agency, the minister said, "In field studies, suspicious samples have been found, which are being investigated... to identify the causes of the students' illness, and the results will be published as soon as possible."

The United Nations human rights office in Geneva called on Friday for a transparent investigation into the suspected attacks and countries including Germany and the United States have voiced concern.

Iran rejected what it views as foreign meddling and "hasty reactions" and said on Friday it was investigating the causes of the incidents.

The string of poisonings come more than five months into nationwide protests following the death in custody of a young Iranian Kurdish woman, 22-year-old Jina Mahsa Amini who had been arrested for an alleged breach of strict dress rules for women.

The demonstrations have posed one of the biggest challenges to Iran's clerical rulers since the 1979 Islamic revolution.

rm,rc/sri (AFP, Reuters, AP)