TEHRAN — Three Iranian police officers and two paramilitary troops were killed overnight during clashes with members of a Sufi Islam order in Tehran, Iranian news outlets reported on Tuesday, the most casualties the security forces have suffered in one evening since the height of antigovernment demonstrations in 2009.

State news media reported that the police arrested more than 300 protesters, most of them members of the Gonabadi dervishes, a mystical Sufi strain of Islam that the clerical government has designated a challenge to mainstream Shiite theology.

The confrontation started Monday night when the dervishes, recognizable by the thick mustaches they wear by religious decree, gathered in front of a police station to demand the release of some members who had been arrested. Violence broke out when security officers arrived.

Photographs posted on social media showed several dervishes who had been severely beaten, though the authenticity of the images could not be independently verified. The clashes were also captured on a murky video spread on social media and broadcast by the semiofficial Fars news agency, which has links to the Islamic Revolutionary Guards Corps.