By Frances Harrison
BBC News, Tehran
Two thousand young men in Iran have protested against new clothing curbs, reports say, amid growing discontent about a crackdown on un-Islamic dress.
More than 100 women were arrested on the first day in Tehran alone
Shiraz university students were angry about new rules banning sleeveless T-shirts, even inside all-male dorms.
The protest came as the judiciary head warned police that an excessively ferocious campaign could backfire.
Police say they stopped more than 1,300 women for dressing immodestly on the first day of the campaign in Tehran.
More than 100 women were arrested on Saturday; half of them had to sign statements promising to improve their clothing, the other half are being referred to court.
Foreign journalists have been prevented from filming women being arrested for un-Islamic clothing
The focus of the new campaign is to stop women wearing tight overcoats that reveal the shape of their bodies or showing too much hair from beneath their headscarves.
However, young men have also been arrested for sporting wild hair styles or T-shirts considered immodest.
Local news agency reports say the protesting Shiraz students on Sunday night were calling for the resignation of the university chancellor.
There is always a crackdown at the start of summer as women start wearing more skimpy clothes because of the hot weather.
Women are banned from wearing short, figure-hugging outfits
In past years the pressure quickly relaxed - headscarves become perched on the back of heads, while fashionable women in affluent north Tehran wear open-toed sandals, three-quarter length trousers and short skin-hugging overcoats.
The police complain that some young women strut the streets looking like fashion models - and it is not a bad description.
But this year the crackdown seems more serious.
Iranian television has broadcast nightly programmes warning women and young men with sleeveless T-shirts and spiky hair to be more careful about their dress.
The newspapers are full of pictures of women being arrested for their un-Islamic clothing, but foreign journalists have been prevented from filming it.
The head of the Iranian judiciary, Ayatollah Shahrudi, has warned that a severe crackdown on un-Islamic dress could have the reverse effect.
The crackdown is more serious than in past years
Meanwhile, an MP has asked why the police should spend so much time arresting young people and filing court cases against them instead of fighting drug addiction and poverty.
Already taxi drivers say there are fewer women on the streets and it is clear most are dressing more conservatively.
It is not just the young and very fashionable who are being harassed this year, middle aged women and even foreign tourists are being cautioned.
One foreign journalist was stopped and the police complained the photograph in her press card was indecent, even though it was taken by the Ministry of Islamic Guidance.