More than 100 students were hospitalised in Iran after a new spate of suspected gas attacks on girls' schools Wednesday, media outlets in the Islamic republic reported.

Hundreds of cases of respiratory distress have been reported in the past three months among schoolgirls across Iran, in what one government official has said could be an attempt to force the closure of girls' schools.

At least 10 girls' schools were targeted in the latest suspected attacks on Wednesday, seven of them in the northwestern city of Ardabil and three in the capital Tehran, media reported.

The incident in Ardabil forced the hospitalisation of 108 students, all of whom were in stable condition, said Tasnim news agency, which also reported poisonings at three schools in Tehran.

Citing parents, Fars news agency said students at a high school in the capital's western neighbourhood of Tehransar had been exposed to a toxic spray. It did not elaborate.

Fars said the security forces had detained three people in the first reported arrests over the wave of suspected poisoning attacks on girls' schools.

Since the outbreak of the mysterious poisonings in November, almost 1,200 students have required hospitalisation for breathing difficulties, a lawmaker said Wednesday.

They included nearly 800 in the holy city of Qom, south of Tehran, and 400 in the western city of Borujerd, said Zahra Sheikhi, spokesperson for the Iranian parliament's health committee.

Health ministry tests on the substance found at the schools in Qom detected traces of nitrogen, which is mainly used in fertilisers, the parliament's website said.

The poisonings have provoked a wave of anger in the country, where critics denounced the silence of the authorities in the face of the growing number of affected schools.

On Sunday, Iran's deputy health minister, Younes Panahi, said some people had been poisoned in Qom with the aim of shutting down education for girls.

Activists have compared those responsible for the attacks on schools to the Taliban in Afghanistan and the Boko Haram in the Sahel, who oppose girls' education.