The Head of the Department of Islamic Guidance in the Iranian city of Mashhad has been arrested after people danced at an event in a local shopping centre.
A video showed a crowd of men and women enjoying a performance by a singer.
Mixing between the genders and dancing in public are severely restricted under Iran’s Islamic laws.
After the footage was shared online, hardliners in Mashhad expressed outrage and called for those who authorized the event to be held accountable.
Under Iranian law, women can be arrested for failing to cover their hair in public.
Dozens of women have been detained in recent months for protesting against the law by removing their headscarves.