Iranian authorities say three police officers have been killed in clashes with followers of a Sufi Muslim religious community in Tehran.
Official media quoted police spokesman Saeed Montazer al-Mahdi as saying on February 19 that the police officers were "martyred in the street in a vicious attack using a bus."
He also said that the "murderers were arrested seconds after their crime."
The hard-line Fars news agency reported that several police officers were also wounded in the incident and hospitalized.
Footage circulating on social media appeared to show the moment the bus plowed into a group of police officers in northern Tehran. The video's authenticity could not be verified.
Authorities said police fired gunshots and tear gas to disperse the demonstrators, who were said to be members of the Sufi Gonabadi order, known as dervishes.
They were protesting outside a police station against the arrest of members of the sect, according to social-media reports.
"The law enforcement forces arrested a number of dervishes and ended the protest by firing tear gas," Mohsen Hamedani, the security deputy of Tehran's governor, told the official IRNA news agency.
Unverified footage on social media showed riot police running through the streets and clashing with black-clad protesters.
Foreign rights groups have accused Iran of persecuting the Gonabadi Sufis over the years.
Sufism, a mystical branch of Islam, is not illegal in Iran but rights groups accuse the Iranian government of harassment and discrimination against their followers.
Several dervishes have been arrested in the last two months, according to the New York-based Center for Human Rights in Iran.
In March 2017, the UN special rapporteur for Iran expressed concern over the state targeting of members of Sufi groups, saying they "continue to face arbitrary arrest, harassment, and detention and are often accused of national security crimes."
With reporting by Reuters and AFP