Police detained 180 people in a western Iranian city after unrest involving Sufi Muslims, the semi-official Fars News Agency reported.
Details about Saturday night's incident were unclear and could not be independently confirmed.
Sufi Muslims have in the past clashed with the authorities in predominantly Shi'ite Muslim Iran.
Sufism, a form of mystical Islam, is tolerated in Iran but some of its religious leaders have called for a clampdown on the group.
Fars News Agency said the trouble began when Sufis attacked a mosque in Boroujerd, about 320 km southwest of Tehran, prompting scuffles between Sufis and their opponents.