Boris Johnson has branded the violence during the Bristol protest as "disgraceful" after protesters hurled glass bottles and bricks at officers, and launched fireworks at police horses.
The Prime Minster posted on social media that the police and the city had his full support as officers say they are concerned more disorder could follow.
He tweeted: “Last night saw disgraceful attacks against police officers in Bristol.
“Our officers should not have to face having bricks, bottles and fireworks being thrown at them by a mob intent on violence and causing damage to property. The police and the city have my full support.”
Home Secretary Priti Patel called some of the protesters who clashed with police "thugs" who were "only intent on causing trouble".
She tweeted: "I am disgusted by the disorder in Bristol and the violence being directed towards the police.
“I’m in no doubt the silent, law-abiding majority will be appalled by the actions of this criminal minority.
“Despite repeated warnings to disperse, it’s clear these thugs were only intent on causing trouble.”
Around 300 people initially joined a march to rally against the government’s Police, Crime, Sentencing and Courts Bill. The crowd marched through the city centre and headed towards Bridewell Street.
By the evening, there were more than 1,000 people standing or sitting near Bridewell police station.
Avon and Somerset Police said glass bottles, bricks and eggs were thrown at officers and fireworks were launched at its mounted division, with one horse being daubed with paint.
Protesters were also pulling at officers’ shields while lasers were shone in their faces, the force said.
Superintendent Mark Runacres said in a statement: “The majority of people acted peacefully however there was a minority who showed hostility to officers.
“This violent conduct is not acceptable.
“Officers repeatedly encouraged people to disperse but once the atmosphere changed and people became physical it was necessary to take action.”
But police have also been accused of being heavy handed. Daily Mirror journalist Matthew Dresch tweeted a video showing a row of police officers advancing.
One of them appears to hit him and the reporter shouts: "What you doing? I'm the press."
Avon and Somerset Police said it was trying to contact Mr Dresch.
In a statement on Twitter, the force said it was aware of the video, adding: “A free press is a cornerstone of our democracy and we fully respect the media’s vital role in reporting events fairly and accurately.”
Supt Runacres added: “All the officers policing the incident are specially trained and accredited in public order and showed exceptional patience in the face of a significant disorder.
“At times reasonable force had to be used – this is not something we ever want to do but we have a duty to uphold the law, prevent crime, and protect people and property.”
Three of those arrested were also detained in connection with last Sunday’s first march, which was followed by another violent demonstration on Tuesday night.
Police had previously urged people not to attend, and later to go home due to the risk of spreading Covid-19.
There was a large police presence at the demonstration. Horses and dogs were used to help move the crowd back.
Earlier in the day, protesters were spotted dancing to music despite heavy rain, handing out flowers and chanting slogans such as “Who do you protect?” and “Justice for Sarah” in reference to Sarah Everard.
Rows of officers and vans had blocked the protesters from Bridewell police station, the scene of Sunday’s violence.
The Police, Crime, Sentencing and Courts Bill, which protesters are fighting against, would give police in England and Wales more power to impose conditions on non-violent protests, including those deemed too noisy or a nuisance. If the bill goes through, convicted protesters will be liable to fines or jail terms.
The first demonstration last Sunday began peacefully with around 3,000 attending, but descended into a riot when some 500 people marched on Bridewell police station.
Nine people were arrested in connection with the disorder last weekend, in which officers were attacked, police vehicles were set on fire and the windows of a police station smashed.
The force later retracted claims two officers suffered fractures in Sunday night’s riot.
A spokesperson for the force said: “We believed the information had been verified but it had not, and while we apologise for that there was no intention to mislead."
A second protest took place on College Green on Tuesday night and led to 15 people being arrested.