Eight police officers were injured during a central London march protesting against the lockdown and Covid-19 vaccine passports.
According to the Metropolitan Police, missiles including bottles were thrown “in small pockets of disorder” as the officers tried to disperse crowds that had gathered in Hyde Park on Saturday.
It added that two officers were taken to hospital but were “not believed to be seriously injured”.
Five people were arrested for offences including assault on police officers, the Met added.
Photos posted on social media appeared to show two police officers – a male and female – with cuts to their face and head.
Other footage posted showed tussles between groups of protesters and the police.
Home Secretary Priti Patel said: “Our brave police are the best of us and should not be the target of senseless violence by a criminal minority for just doing their job.
“I am getting tough on these thugs and will be doubling the sentence for assault of an emergency worker. I wish the officers a speedy recovery.”
Ken Marsh, chairman of the Metropolitan Police Federation – which represents thousands of rank-and-file Scotland Yard officers – said: “We can assure everyone that we shall be raising the scenes we witnessed in Hyde Park yesterday with senior management in the Metropolitan Police with utmost urgency.
“The safety of our police officers should be top of the agenda. We wish all our injured colleagues a swift recovery and will be supporting them as best as we can.”
He added: “Peaceful protest may well be the cornerstone of democracy – and police officers have a role in facilitating that – but the scenes we saw in Hyde Park yesterday of a thin blue line of brave and sadly bloodied police officers coming under attack from thugs were anything but peaceful.
“Police officers are human beings who go out every day to keep people safe. Many people seem to have forgotten that right now but we will keep reminding them.
“Our colleagues have every right to go home to their families at the end of their shifts. Not to hospital.”
The crowd at the anti-lockdown protest, estimated to have been around 10,000 strong, included Laurence Fox, a fringe candidate running for Mayor of London. Piers Corbyn, who is also standing in the London mayoral election, was also photographed at Hyde Park.
Protesters at the march defied social-distancing rules to attend and carried placards with messages including: “no to vaccine passports”, “no mask, no vax, no lockdown”, “free your face do not comply” and “we do not consent”.
The march was organised by the Unite for Freedom group and others critical of Covid-19 restrictions.
The government plans to trial Covid passports to see how crowds could return to large events in England, including the theatre, nightclubs, and sports events.
However, dozens of MPs have criticised the proposals for vaccine passports as “dangerous, discriminatory and counterproductive” . By Jane Clinton, Inews