In Iran women are legally required to dress modestly and ensure their hair is covered.
A series of acid attacks on women in the historic Iranian city of Isfahan has raised fears and prompted rumors that the victims were targeted for not being properly veiled.
Police have declined to comment on a motive but suspects have been arrested and an investigation is ongoing, General Hossein Ashtari was quoted as saying by the official IRNA news agency.
He said four acid attacks had been reported in Isfahan, 450 kilometers south of Tehran, but he gave no other details.
The violence led to chatter on social networks that there had been up to 13 acid attacks against women drivers who were “badly veiled” with accompanying warnings against leaving car windows open.
Such incidents have risen in recent years in Pakistan, Afghanistan and India, with the abusers claiming they punished women for “sullying” their family “honor” by committing “indecent” behavior.
Under Islamic law in force in Iran since the 1979 revolution, women must wear loose clothing, known as hijab, that covers the head and neck.
Recent years, however, have seen many wear a thin veil that hardly covers the hair and tight clothing or coats reaching mid-thigh - an ensemble often denounced by conservatives as “bad hijab” - instead of a traditional chador that covers the whole body.
A senior cleric of Isfahan, considered Iran's top tourist attraction for its carpets, ancient mosques and giant square - second only in size to Tiananmen Square in Beijing - condemned the attacks.
“Such an act under any pretext is reprehensible,” Hojatoleslam Mohammad Taghi Rahbar, a Friday prayers leader, told the ISNA news agency.
“Even if a woman goes out into the street in the worst way, no one has the right to do such a thing,” he said.
A fearful resident of the city was quoted by ISNA as saying: “I roll the windows closed and I panic every time I hear the sound of a motorcycle approaching.”
Iranian MPs have written to President Hassan Rowhani in recent months to demand that police better enforce wearing of the veil.
Nasser Jowrkesh, whose daughter Soheila was one of the victims, told BBC Persian: "The attack caused extensive acid burns on her face, forehead, both hands and legs.
"She has lost her complete eyesight on her right eye. Regarding her left eye an ophthalmologist and surgeon in Labbafi Nejad hospital believes that there is a narrow hope to save some 25-30% of her eyesight."
Pictures on Irna's website showed women wrapped in bandages lying on hospital beds.
Hardliners within Iran's conservative-dominated parliament have been trying for the past few months to pass a bill that would protect vigilantes trying to enforce Islamic law.
But those allied to Iran's moderate President Hassan Rouhani have opposed such legislation.
An Iranian woman blinded and left seriously disfigured after having acid thrown in her face has pardoned the man responsible, state television has reported.
Majid Movahedi threw acid in Ameneh Bahrami's face in 2004 after she refused his offer of marriage.
A court hearing in 2008 backed her call for qisas, a rarely-used form of retributive justice in Sharia law.
Hundreds of protesters gathered in front of the parliament building in Tehran, and thousands more in Isfahan City, where at least six women are believed to have suffered acid attacks in the last few weeks.