Iran has declared rap music illegal and says it will hunt down rap artists who attempt to reach local audiences.

"There is nothing wrong with this type of music in itself," the official for evaluation of music at the culture and Islamic guidance ministry told Iran's IRNA news agency.

"But due to the use of obscene words by its singers this music has been categorized as illegal," he said.

Rap music has become popular among young urban men, especially in the capital Tehran.

Western rap music is widely available on the black market and local artists are being inspired by the Iranian exile community in Los Angeles to rap about social and political issues.

But local artists must work underground as Iran forces musicians to gain permission from the culture ministry to produce albums and hold concerts.

The ministry decried the practice of releasing music on the internet and thereby bypassing the government, and said it had already identified a large number of illegal rap singers.

Illegal studios will be closed and rap singers "confronted," the ministry said in its edict.

The Islamic republic's hardline officials have repeatedly complained about a "cultural invasion" by "decadent" Western music, which they believe contravenes Islamic values.

Iran is in the midst of a crackdown on Western books and TV shows that are considered decadent, and has stepped up warnings against women who are not covered enough to satisfy Islamic hardliners.

With files from Australian Broadcasting Corp.