The Iranian government wants to maintain Islamic values

The Ministry for Culture and Islamic Guidance said illegal studios would be closed and rap singers "confronted".

An official condemned rappers for using very vulgar words, but it was not clear if the whole genre was being banned.

Rap music in Farsi is increasingly popular among young men in Tehran, with lyrics covering political, social and sexual themes.

Iranians wanting to record an album or stage a concert need to get official permission.

Some songs are approved by the ministry, but most are circulated through a growing underground market for rap.

The culture ministry official, Mohammad Dashtgoli, was quoted by the official Irna news agency as saying he wanted to "find a solution" to internet distribution of the music.

Iranian rappers are inspired by the Iranian exile community in Los Angeles - one of the main centres of American rap.

Young Iranian singers are trying to replicate the accents and subject material used by many US artists.

"Decadence" targeted

The campaign is the latest attempt by the Iranian authorities to stop Western values gaining ground at the expense of traditional Islamic morality, correspondents say.

Earlier this month Iranian newspapers printed a list of vices that the police would target, including "decadent" films, drugs and alcohol.

But their main focus appears to be women wearing make-up and using hats instead of headscarves.

In the last six months, tens of thousands of women have been warned or arrested because of their clothes.

The Iranian Supreme Leader, Ayatollah Ali Khamenei, has publicly backed the police action.