Iranian authorities on Wednesday ordered an investigation into a video showing officials brutally beating a protester that human rights groups said exposed the sheer brutality of the police crackdown on protests sparked by the death of Mahsa Amini.

Iran has been rocked by more than six weeks of protests following the death of Amini, who was arrested by Tehran’s notorious morality police, with the move now seen as the biggest challenge to the Islamic Republic’s leadership since the 1979 revolution.

Activists say a crackdown by security forces has killed dozens and arrested thousands accused of shooting at close range, beating protesters with batons and other abuses.

A video that surfaced on social media late Tuesday, allegedly taken with a mobile phone in a Tehran neighborhood at night, showed a group of around a dozen police officers in an alley, kicking and hitting a man with their batons while others Officers on motorcycles looked on.

The man first tried to cover his head with his hands before a gunshot is heard and he is run over by a police motorcycle. His motionless body is then abandoned.

“This shocking video from Tehran is another horrific reminder that the cruelty of Iran’s security forces knows no bounds,” Amnesty International said.

“Amid a crisis of impunity, they are free to brutally beat and shoot protesters,” she added, calling on the UN Human Rights Council to “urgently investigate these crimes.”

Iranian police said in a statement released by the state news agency IRNA that an order had been issued to “determine the exact time and place of the incident and to identify the perpetrators.”

“Police have absolutely no condonation for violent and unconventional behavior and will deal with offenders according to the rules,” the statement added.

According to an updated figure released Wednesday by the Norway-based Iranian human rights NGO, 176 people have been killed in the crackdown on protests sparked by Amini’s death.

Another 101 people were killed in a widespread protest wave in Zahedan in the south-eastern province of Sistan-Balochistan.

The IHR has warned that these numbers are a minimum as the information is slow to flow due to disruptions to the internet by the authorities.

Thousands of people have been arrested across the country in the crackdown on protests, rights activists say, while Iran’s judiciary said 1,000 people have already been charged in connection with what they describe as “unrest”.

The trial of five men charged with crimes that carry the death penalty opened in Tehran on Saturday.

“Instead of accepting the people’s legal demands, the Islamic Republic is getting away with repressive measures and show trials,” said IHR director Mahmood Amiry-Moghaddam.

“The charges and sentences have no legal force and their only purpose is to commit more violence to create social fear,” he added.

Amini’s death was caused by a blow to the head while in custody, according to family members. The Iranian authorities denied this explanation and later denied it in an official medical report.

The protests have been fueled by anger at Iran’s strict Islamic dress code for women – which the police who arrested Amini enforced – but have become a rallying point for popular anger against the regime that has ruled Iran since the fall of Iran Shahs reigns in 1979.

While protests have erupted in Iran over the past two decades, the current movement has regularly broken taboos, united social classes, and spread largely across the country.

The challenge to the regime is compounded by Iran’s custom of observing 40 days since a person’s death, making any 40-day “chehelom” mourning ceremony for the dozens killed in the raid a potential focus of protest becomes.

“Funerals and 40-day memorials for slain protesters are increasingly becoming the impetus for further unrest,” said Kita Fitzpatrick, an Iran analyst with the American Enterprise Institute’s Critical Threats Project.

“This puts the regime in a bind: it risks inadvertently supporting the protest movement by trying to violently repress it.”