South African authorities Friday arrested eight police officers accused of being involved in dragging a man down a road while he was handcuffed to the back of a police van.
Crowds chased after the van as the man kicked and writhed. He later died.
The incident was captured on video, sparking outrage in a nation that has seen a series of police brutality incidents recently.
The country's Independent Police Investigation Directorate on Friday arrested the officers, who earlier had been disarmed and suspended, said Zweli Mnisi, spokesman for police ministry.
Tough action will be taken against those involved, the nation's acting police minister said, calling for a speedy independent investigation.
"We view this incident in serious light. We want stern action so that it may send a message to other officers that any untoward conduct will not be tolerated," State Security Minister Siyabonga Cwele said.
It was unclear how many officers are involved in the incident. The commander of the local police station was also suspended pending an investigation, the South African Police Service said in a statement.
The video was captured by cell phone in Daveyton, near Johannesburg, shocking the world for its brazen cruelty.
Shaky but clear, it shows a man in a red T-shirt and white sneakers talking animatedly with police officers.
The officers then handcuff him to the back of a police van, which pulls away, dragging his feet along the road. Officers and bystanders run alongside.
Some in the crowd scream as the van drives away slowly, then picks up speed.
The man, identified as a Mozambican taxi driver, died Tuesday night, a few hours after the incident, in a police cell from his head injuries, according to Amnesty International.
"We are shocked by this incident," said Moses Dlamini, a spokesman for the Police Investigative Directorate, an independent government agency that looks into possible crimes by police.
Violent crime is common in South Africa, but the incident was a harsh reminder of police brutality rampant in the nation.
The directorate received 720 new cases for investigation of suspicious deaths in custody or in other policing contexts between April 2011 and March 2012, Amnesty said.
"This appalling incident involving excessive force is the latest in an increasingly disturbing pattern of brutal police conduct in South Africa," said Noel Kututwa, Amnesty International's southern Africa director.
Police who carry out crimes do not reflect the police service as a whole, Dlamini said.
"There are many other officers who are dedicated, who uphold the law and arrest criminals all the time," he said.
Under apartheid rule in South Africa, white police officers subjected the nation's black majority to inhumane treatment. But in this case, the man and police in the video, as well as those in the crowd, are black.
Apartheid rule ended in the 1990s, and the government reformed the police departments and made them more diverse.
Despite the changes, the nation grapples with a high crime rate, including rapes, armed robberies and police brutality, analysts say.
South Africa's history of violence "is part and parcel of daily life," said Johan Burger, a senior researcher with the Institute for Security Studies in Pretoria.
Some police officers believe that they "are above the law" and that there won't be consequences for their actions, he said.
South Africa's police force has been plagued by a series of scandals recently.
In August, officers opened fire on striking platinum miners in Marikana, killing 34 in one of the most deadly police shootings since the end of apartheid.
Last month, one of its officers -- Hilton Botha -- was booted from a high-profile murder case after prosecutors reinstated attempted murder charges against him.
Botha is accused of chasing and firing on a minibus full of people while drunk in 2011. He is charged with seven counts of attempted murder.
He was testifying in the trial of Paralympic star Oscar Pistorius, who is charged with killing his girlfriend on Valentine's Day.
In the case of the taxi driver, the independent investigative agency pledged to be transparent in its findings.