Police said 16 people had been arrested and nine officers injured following clashes at anti-coronavirus lockdown demonstrations in central London.
Thousands of people massed in Trafalgar Square on Saturday carrying a variety of signs, flags and placards to take part in a "we do not consent" rally – with none appearing to wear face coverings or to social distance.
The demonstrators, who are protesting against Government coronavirus lockdown measures, cheered and clapped, shouting “we will win”.
But officers clashed with protesters when police tried to shut the event down because crowds were not complying with social-distancing rules.
Bottles were thrown and police used batons against protesters, leaving some with visible injuries.
At least three protesters and one officer were treated by medical staff.
Scotland Yard said 16 people had been arrested following the demonstration, which moved from Trafalgar Square to Hyde Park.
Arrests were for a variety of offences including breaching Coronavirus regulations, assaulting a police officer, public order offences and violent disorder, it added.
A total of nine officers were injured, two of whom required hospital treatment for head injuries, the force added.
London Mayor Sadiq Khan, stressed that large gatherings, including protests, were still banned to stop the spread of Covid-19.
He added: "The reckless and violent behaviour of some protestors has left hard-working police officers injured and put the safety of our city, which is at a critical moment in the fight against this virus, at risk. This is totally unacceptable."
Mr Khan added: "We cannot let the sacrifices Londoners have made be undermined by the selfish behaviour of a small number."
"Violence of this kind towards officers will not be tolerated and perpetrators will feel the full force of the law."
The Metropolitan Police said the protest was stopped because crowds had not complied with social distancing and risked spreading coronavirus.
Commander Ade Adelekan said: "As the crowds began to swell in Trafalgar Square, it became impossible for people maintain social distancing and keep each other safe.
"Likewise, there appeared to be no efforts by organisers to engage with crowds and keep those assembling safe from transmitting the virus."
He added: "This lack of action voided the risk assessment submitted by event organisers the night before."
"This is especially saddening in light of the injuries sustained by officers last weekend."
"Therefore, today’s demonstration was no longer exempt from the Coronavirus regulations."