Violent clashes broke out in Bristol in south-west England on Sunday at a protest against a government bill proposing new policing powers to restrict demonstrations.
Thousands of people converged on the city centre, defying Covid-19 restrictions and ignoring a police appeal to stay away.
What started as a non-violent demonstration turned ugly after hundreds of protesters converged on the New Bridewell police station.
Demonstrators launched fireworks at officers and knocked over a police van, a witness said. Others said officers tried to repel protesters by using batons and shields.
Damage was also caused to the police station.
Two police officers were seriously injured in the skirmish, suffering broken ribs and an arm.
A clean-up operation is now under way to remove broken glass, debris and graffiti from the streets.
It is understood the police operation has cost around £1 million ($1.3m).
Protesters carried placards with slogans such as 'The Day Democracy became Dictatorship' and 'We Can't be Silenced that Easy'.
Avon and Somerset Police chief constable Andy Marsh said on Monday more arrests were expected. Seven people have already been taken into custody on Sunday.
He said police decided against making more arrests on the night to avoid further antagonising the crowd.
"They were looking for a trigger to provoke a violence response," he told the BBC.
He said police would be releasing "hours of CCTV footage" to identify potential protesters.
"We will be asking for the people of Bristol to identify these thuggish citizens so we can bring them to justice," he said.
Bristol mayor Marvin Rees said the "self-indulgent" thuggery would be used to justify the legislation in question.
"I have major concerns about the bill myself, which is poorly thought out and could impose disproportionate controls on free expression and the right to peaceful protest," he said.
“Smashing buildings in our city centre, vandalising vehicles, attacking our police will do nothing to lessen the likelihood of the bill going through.
“On the contrary, the lawlessness on show will be used as evidence and promote the need for the bill. This is a shameful day in an incredible year for Bristol.
“We have faced times of great confrontation particularly surrounding Black Lives Matter and the events that followed.
“We have had numerous protests. Our police, city representatives and I have been able to point out with pride that we have faced these moments of conflict without the physical conflict that others have experienced.
“Those who decided to turn the protest into a physical confrontation and smash our city have robbed us of this.”
Home Secretary Priti Patel tweeted: “Unacceptable scenes in Bristol tonight. Thuggery and disorder by a minority will never be tolerated.
“Our police officers put themselves in harm’s way to protect us all. My thoughts this evening are with those police officers injured.”
Sue Mountstevens, Avon and Somerset's police and crime commissioner, added that the behaviour was "completely unacceptable" and the protest had been "hijacked by criminals".
"It's disgraceful that these men and women who started their days expecting a normal day of policing have all returned battered and bruised," she said.
"These people have shown reckless disregard of the lives and safety of our communities in central Bristol and our officers.
"Whether you agree or disagree with the bill these men and women did not deserve to face the level of violence directed at them. Nothing can justify such actions."
The government's police, crime, sentencing and courts bill, which is still before Parliament, would give police new powers to impose time and noise limits on street protests.
That has angered activists, particularly after a heavy-handed police response to a London vigil for Sarah Everard on March 13 drew widespread criticism.
The serving police officer was charged with Everard's murder and the case has highlighted violence against women and girls.
Although it is yet to be passed as legislation, the government bill was introduced before the Everard case and covers a wide range of matters including policing protests.
But the two became connected in many people's minds because the bill was up for debate in Parliament two days after the London vigil.
