The unrest in the streets was sparked when about 160 officers in full riot gear swooped on a house in Bristol to arrest four people they said were "a real threat to the local community".
Eight officers were injured in the disturbance during which they were involved in what eyewitnesses described as running battles with hundreds of protesters.
The crowd dug up cobbles from the road surface to throw at the police and a nearby branch of Tesco Metro was petrol-bombed.
The supermarket opened a week ago despite some opposition in the local Stokes Croft neighbourhood, which includes a number of squats and few chain stores.
Jessie Webb, a barman at The Croft pub, said the police were "heavy-handed" towards a crowd which initially just turned up to watch the operation to arrest the people in the house.
He said: "The police caused it (the riot). They turned up in large numbers and it attracted a crowd. Then they charged into them."
A 22-year-old, who did not want to be named, said he was hit with a baton despite not being involved in the protest.
"I saw them (police) hitting people who were definitely not involved in the violence," he said. "They were doing random charges and cracking people indiscriminately."
But Avon and Somerset Constabulary said the actions they took during the "robust operation" were fully justified.
The trouble erupted after the officers descended on the property in Cheltenham Road at about 9.15pm last night.
Assistant Chief Constable Rod Hansen, defending the operation, said: "Residents have called us to several incidents in the property over the past few days.
"Yesterday there was a very real threat to the local community from the petrol bombs that were being made and we needed to take positive action.
"The safety of the public is paramount in any situation of this kind and we took the decision to carry out a swift arrest operation, following intelligence received about the criminal intentions of those who were occupying the building.
"The fact that we seized petrol bombs illustrates the seriousness of this situation and the reason why we took this positive action."
Some 300 people had congregated however, a minority of whom started small fires and began throwing bottles, stones and other items at officers, he said.
"We used well-rehearsed plans, which involved the use of officers from neighbouring forces, to control what had become a volatile situation," he added.
The riot was brought under control at around 4am.
Three people were arrested on suspicion of public order offences and another person on suspicion of threats to cause criminal damage with intent to endanger life.
Primary school teacher Nick Jones, who watched the scene unfold, said what started as a peaceful protest quickly turned ugly.
Gangs from other parts of Bristol may have joined in, he suggested.
"People came from different areas, hearing what was going on," he said. "It turned into a running battle up and down the street for two hours.
"Between 2.30am and 4.30am there were bottles thrown and rocks. I saw a police officer get hit in the face and go down - he was taken away in an ambulance.
"People had weapons. They had saws and shields themselves. It turned from 'interesting' to 'scary' very quickly."
Eyewitness Alex Slocombe said: "We went down Picton Street and that is where it became quite heated. We were pushed back down the street by a lot of police.
"Then there was a surge of people who pushed the police back up Picton Street. It was still peaceful but it was starting to bubble up.
"The police were pushed back down Ashley Road. That was when it became more heated. There were running battles with the police.
"The police looked like they didn't know what to do. They were being surged at from all sides."
Local people said the Tesco in Cheltenham Road was not petrol- bombed but had been damaged by a crowd who tried to overturn a police car outside.
The supermarket was closed today while the damage was assessed.
A spokesman for the chain said: "We strongly condemn the violence in Stokes Croft and the injuries caused to the members of the police who worked courageously to protect the public and businesses in the area, including ours.
"We will work hard to reopen as soon as possible to continue providing a service to Stokes Croft."
A heavy police presence remained in the area today, including officers and riot vans.
