Iran's government has launched a crackdown on women who flout the strict Islamic dress codes during the hot summer months.
Police chief in Tehran General Morteza Talaei has warned that anybody caught involved in what he called social corruption will be punished.
The authorities have found it difficult to enforce such measures in the past.
It comes after conservatives beat reformists in controversial general elections in February.
In keeping with Islamic values, Iranian women are required to cover their hair entirely and wear long, loose clothing to disguise the shape of their bodies.
Offenders could risk fines, prison and even flogging.
Raids
But during the scorching summer months, when in many Iranian cities the temperature goes above 40C, observing such strict rules becomes unbearable for many women.
The hardline police chief in Tehran said his force was now determined to enforce the Islamic measures and punish the offenders.
Such announcements are usually common at the beginning of summer when many women defy the rules by wearing shorter, tighter and brighter coats.
But reformist politicians in Iran fear that this time the conservatives - who have reasserted their power after general elections, in which many pro-reform candidates were banned from standing - may really intend to try to enforce such measures.
Reports say that in recent weeks raids on mixed-sex parties and coffee shops, where young people flirt over a burger or coke, have increased.
But most observers say the crackdown would be counter-productive in a country where two-thirds of the people are under 30 and women play an important role in society.