Iranian security forces, including the pro-government Basij, are trying to quell growing, nationwide protests that erupted last week after a woman died in police custody.
Four members of the Basij were killed in the unrest, including one who was stabbed, Iranian media reported.
Here are some facts about the Basij, shock troops that have been at the forefront of repressing popular unrest, making them a direct target for protesters angered by the lack of political and social freedoms in Iran.
The Basij, formally known as the Organisation for the Mobilisation of the Oppressed, was created as a paramilitary volunteer militia by the founder of the Iranian revolution, Ayatollah Ruhollah Khomeini, in 1979.
Most Basijis come from poor, rural backgrounds, and are known for their “human wave” attacks against Saddam Hussein's troops in the 1980-1988 war with Iraq, which were intended to overwhelm the enemy by the sheer weight of numbers, regardless of high casualties.
In peacetime, they enforce Iran’s Islamic social codes, acting as morality police at checkpoints and in parks, and at other times crushing protests. The force is also deployed during natural disasters and has a presence in government institutions.
Analysts say Basij volunteers may number in the millions, with one million active members.
In 1981, the Basij was incorporated into the organisational structure of the Revolutionary Guards, the main paramilitary force in charge of protecting the Shiite clerical ruling system and revolutionary values.
After Iran's war with Iraq ended in 1988, the Basij were not disbanded and continued as a religious militia that provides the country’s establishment with manpower and a heavy presence during pro-government rallies.
The morality police are often made up of and backed by the Basij, which acts as the state's iron fist when protests erupt.
The Basij have a presence in every Iranian university, monitoring people's dress and behaviour, as higher learning is where Iranian men and women meet for the first time in a mixed educational environment.
A Basiji usually belongs to parts of Iran's religiously traditional and pro-regime youth. They are closely affiliated with the country's hardline faction and represent one hand of Iran’s own culture war, which pits conservative and more liberal citizens against each other.
Role in latest demonstrations
Semi-official media outlets have reported the death of at least five security personnel in different Iranian cities over the past week, including four members of the Basij.
Pro-government media said the killed security forces had been attacked by “rioters and gangs” while trying to enforce order and stop protesters from destroying public property.
One Basij died from stab wounds while another was shot, local media reported.
Fars news, an agency close to the Revolutionary Guards, shared a video on Telegram showing the Basij at work during the current unrest.
The footage showed the volunteers putting out small fires in waste containers as they cleaned up streets after the protests.
Basijis interviewed in the video said “rioters” had closed roads in the capital city, endangered ordinary people, destroyed public property and removed the veils of religious women.
They added they were mobilised late at night to protect the “honour and property of the people” and that they would not allow “a few sissies” to disrupt the order of the country.
“We will stand till the end [to protect the regime],” one was heard saying in the footage.
Reuters could not verify the video.