More than 5,000 cases of poisoned school pupils have been reported across the country, an Iranian MP said, as attacks spread to public transport networks.
The poisonings were a result of "special gas", MP Mohammed Hassan Asefari told the Iranian Students' News Agency.
The number those affected was significantly higher than official estimates of about 1,000.
The Czech Republic-based Radio Farda reported around 2,500 cases in more than 100 schools, according to Iranian media outlets.
First reported in the holy city of Qom in November, the poisonings have increased in recent weeks and prompted renewed anti-government protests and pushed parents to take their children out of school.
While authorities have placed the blame with Tehran's enemies, many accuse the government, pressured by months of fierce protests, of being behind the attacks.
Parents gathered outside the Ministry of Education at the weekend, in video footage verified by Reuters.
"Basij, Guards, you are our Daesh," they chanted, likening security forces to ISIS.
The Islamic Revolutionary Guard Corps and its Basij paramilitary force have been at the forefront of the regime's response to the protests and are estimated to have killed more than 500 people since demonstrations began in September.
Pro-protest accounts also reported renewed rallies in several areas, with people demonstrating against the "baby-killing government".
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Demonstrators chant slogans during the March of Solidarity for Iran in Washington. AFP -
Another group of demonstrators at the march. AFP -
A protest in support of Iranian women in Barcelona. Reuters -
Iranian citizens and locals joined in the Barcelona protest. Reuters -
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People wave the Shah-era Iranian flag during a protest in Paris. AFP -
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Protesters take to the streets of Tehran. EPA -
Iranian protesters run after clashing with with police. EPA -
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Iranians living in Athens hold a protest in solidarity. AFP -
People take part in a rally in The Hague. AFP -
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Members of feminist groups and Iranian migrants during the protests in Santiago. AFP -
Iranian activists shout slogans during a protest against the government in Tehran, in Amsterdam, The Netherlands. EPA -
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A woman cuts her hair during the protest in front of the Iranian embassy in Madrid. Reuters -
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A protest in Nantes, western France, after the death of Amini in Iranian police custody. AFP -
Women gather for a demonstration in Barcelona, Spain. AFP -
Demonstrators in Nantes. Amini's death has sparked a global protest movement. AFP -
Women protest outside the town hall in in Montpellier, southern France. AFP -
A woman at a protest in Catalunya Square, Barcelona. Reuters -
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In Barcelona, protesters take part in a demonstration in support of Iranian women. AFP -
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A woman in Istanbul cuts her hair during a protest against Iran. Getty -
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Demonstrators hold placards in Mexico City during a protest against Iran. Reuters -
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Iranian Americans participate in a rally in central Los Angeles, in solidarity with women in Iran. AP -
Demonstrators march during a protest in Los Angeles, California. AFP -
A woman with the colours of the Iranian flag painted on her face participates in a rally as thousands demonstrate in support of Iranian women in Los Angeles. EPA -
Australians protest over Amini's death in Melbourne. EPA -
Police block protesters from entering Iran's embassy in Oslo, Norway. EPA -
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A candlelight vigil for Amini in Los Angeles. AFP -
Afghan women hold placards as they take part in a protest in front of the Iranian embassy in Kabul. AFP -
Protestors take part in a rally outside the Iranian consulate in Istanbul. AFP -
An Iranian woman shows a lock of hair she cut off during a protest outside the Iranian consulate in Istanbul. EPA -
Demonstrators outside the Iranian consulate in Istanbul. Getty -
Iranian Americans rally on Capitol Hill in Washington to show support for protesters in Iran. AFP -
Protesters on Capitol Hill hold a sign condemning the crackdown by Tehran. AFP -
German demonstrators gather in Berlin after the death of Amini in Iranian police custody. AP -
A protester cries during a rally in Berlin. Reuters -
A demonstration in Madrid, Spain. Thousands have gathered in cities across Europe to support protests in Iran. AP -
Demonstrators gather outside the Iranian embassy in Madrid. Reuters -
People take part in a protest in Lausanne, Switzerland. EPA -
Protesters hold signs featuring images of Amini during the protest in the western Swiss city. EPA -
Demonstrators in front of the Iranian embassy in Buenos Aires, Argentina. EPA -
An activist outside the Iranian embassy in Buenos Aires, Argentina, with a sign that reads 'Justice for Mahsa Amini'. AFP -
A demonstration against violence in Iran is held in Quito, Ecuador. The Iranian community in Ecuador protested outside the Iranian embassy. EPA -
Protesters at a demonstration outside the Iranian embassy in Quito, Ecuador. EPA
Schoolgirls are said to be the most affected but cases have also been reported at universities and at boys' schools.
The health ministry has claimed that "no toxic traces" were found in medical samples taken from students at affected schools.
Supreme Leader Ayatollah Khamenei said those responsible should be executed.
The poisonings have been widely condemned and the US has said it may fall under the mandate of a UN investigation.
While the government has pledged a full investigation, it has opened legal cases into news outlets for "spreading lies" about the attacks which have left some students in critical condition.
The judiciary has opened lawsuits against six news outlets and media personalities for "publishing lies and baseless rumours", its affiliated news agency Mizan reported.
Wider target
Special branches have been set up across the country to deal with false rumours, it announced on Monday, and two additional branches have been established within Tehran's Special Prosecutors Office.
Meanwhile, people have also reported poisonings at metro stations in several cities, prompting fears the attacks could target wider society.
Footage on social media show travellers coughing and collapsed on metro platforms, while others have published images of emergency hammers removed from carriages, claiming they fear it is a prelude to similar attacks.
Civil rights advocate Atena Daemi also alluded to possible attacks on the metro.
"The Islamic Republic collected emergency hammers and replaced the subway windows, which is a warning for more extensive chemical attacks by government agents," said Ms Daemi, who has been imprisoned in Tehran's notorious Evin prison and has a wide following on social media.
On Tuesday, social media users warned people away from a metro station in the city of Isfahan, claiming passengers had begun collapsing and vomiting, while people reportedly fainted at a Tehran station.
