BEIRUT: It is a question all Iranians are asking: who is stalking the streets of Isfahan, throwing acid into women's faces? The attacks - there have been at least four in the busy city in central Iran in recent weeks - appear aimed at terrorizing women who dare to test the boundaries of the Islamic dress code.
The crimes coincided with the passage of a new parliamentary bill that allows private citizens to enforce "morality" laws.
The bill has sparked a clash between hardline politicians, who overwhelmingly support it, and moderates including President Hassan Rouhani.
The split is an illustration of the wider political challenges Rouhani faces from his hardline opponents. Acid attacks - an excruciating assault used in many countries to rob women of their looks - are rare in Iran and authorities, including conservative clerics, were quick to condemn them.
But in a country where volunteer militia operate as the self-appointed guardians of Islamic behaviour, it is inevitable that suspicions have fallen on religious vigilante groups – so much so that one issued a statement to deflect accusations.
Ansar-e-Hezbollah, a plainclothes militia which has conducted 'morality patrols' to enforce Islamic dress, blamed "the enemy" for the acid attacks that it said were carried out to "strike a blow against security."
Attempts to reach the group for further comment were unsuccessful. Police have arrested a handful of suspects but not yet charged anyone.
Thousands of people took to the streets of Isfahan, and hundreds in Tehran, two weeks ago to protest that not enough was being done to find the assailants.
Local media, which have suggested there may have been twice as many attacks as officially confirmed, said some Isfahani women had received text messages threatening them with attack if they did not respect the dress code, or hijab, which in Iran means covering the hair and wearing modest clothing.
"If you don't observe your hijab, then you will be sprayed with acid," read one anonymous text message received by a women that the Iranian Students' News Agency, identified as Haniya.
"If the acid spraying is related to hijab, then why aren't the authorities giving their views about this?" she said.
Special police units are often deployed in Iran's cities to enforce the hijab, pulling aside women they consider to be overly made-up or allowing their hair to spill out from underneath the obligatory headscarf.
But groups like Ansar-e-Hezbollah have also long played a role in enforcing social laws, pressuring women to dress more conservatively or confronting unmarried couples who appear in public together.
They have also helped the government crack down on political dissent, such as during the protests which followed the disputed 2009 presidential elections.
Though officials have denied links with these militant groups, there is an overlap between their activities and that of the Basij, a militia that is overseen by the Islamic Revolutionary Guard Corps, experts say.
The acid attacks happened as Iran's conservative-dominated parliament was passing its morality bill, which essentially gives legal protection to groups like Ansar-e Hezbollah that seek to enforce Islamic behaviour.
That bill, which critics say will give free rein to vigilantes, has drawn a battle line between the hardliners and Rouhani, who has struck a moderate tone on social issues.
"We can't just treat one issue, bad hijab, as the ultimate evil from morning to night," Rouhani said in a speech two weeks ago in which he implicitly criticised the bill, according to the Shargh newspaper.
"Iranian women are Muslim women of virtue who are all supporting hijab. So a few people in this country should not consider themselves the custodians of morality," said Rouhani, himself an Islamic cleric.
By that time, parliament had already passed the bill. "This definitely does seem to be a slap back at Rouhani by the parliament," said Faraz Sanei, Iran researcher for New York-based Human Rights Watch.
"The Rouhani administration is clearly on the record as being very, very sceptical of Ansar-e-Hezbollah and enforcing of morality laws by vigilante groups."
In a small victory for the Rouhani administration, Ansar-e-Hezbollah called off plans to start morality patrols in Tehran in September, after the interior ministry said anyone carrying out such activities would need permission from the government.
The morality bill still faces some final hurdles before becoming law, but the support of parliament is a boost for militia groups and a blow to Rouhani, according to Amir Farshad Ebrahimi, a former member of Ansar-e-Hezbollah who now works as a journalist in Germany.
"They're actually giving them (militia groups) a green light," he said. "As long as Rouhani's government is in place they'll continue their activities. Social freedoms, like wearing hijab,have become the Achilles heel of the Rouhani government."
While Rouhani has disappointed liberals who say that he has delivered little social reform, conservatives are using his moderate rhetoric on issues like hijab to paint him as seeking to distance Iran from the ideals of the Islamic revolution.
"Rouhani has been more vocal on these issues than he has on lots of other issues," said Sanei from Human Rights Watch. "That just seems to make it worse. It seems to stoke the fires in parliament even more to push back against him and his administration."
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