"A number of women attended the ceremony without wearing the hijab, and ethical and legal standards were not observed," the judiciary's Mizan Online news website said.

The Tehran prosecutor's office announced "legal action against all organisers, performers and people who committed acts contrary to public morality and decency in the venue," it added.

The 12th Iranian Interior Design Awards ceremony was held in the capital's National Library Auditorium on January 20.

Under rules imposed after the 1979 Islamic revolution, women must cover their hair and neck and wear loose-fitting clothes in public.

But many women, especially in Iran's major cities have pushed the boundaries by allowing their head coverings to slide back and reveal more hair.

Iran saw months of nationwide protests after the death in custody in September 2022 of Mahsa Amini, a young Iranian Kurdish woman detained for an alleged breach of the dress code.

Hundreds of people were killed in the unrest, including dozens of security personnel. Thousands of demonstrators were arrested.