Police arrested 23 people during protests in London over the death of African-American man George Floyd in Minneapolis.
Scotland Yard said late on Sunday night the arrests were for a range of offences but did not give further details.
Crowds of demonstrators broke lockdown rules on Sunday to march through the capital and protest in Tralfalgar Square and outside the US embassy over the death of Mr Floyd after he was arrested by police in Minnesota a week ago.
Initially police said there were five arrests - three for alleged breaches of COVID legislation and two after officers were assaulted.
Members of Black Lives Matter defied the Government's ban on mass gatherings to protest in Trafalgar Square and outside the embassy in Battersea.
Aerial pictures showed thousands crammed together outside the south London building as police officers approached.
Many held up signs saying "Justice for George Floyd", who died in after white police officer Derek Chauvin held him down by kneeling on his neck.
The march then moved past the Chelsea Barracks building in Westminster and on to Grenfell Tower in the north west of the city.
One marcher wrote "Black Lives Matter" on the memorial at the base of the tower block, as others watched on in solemn silence.
The US has been rocked with nightly protests since Mr Floyd's death in Minneapolis last Monday, with at least 1,600 people arrested in 22 cities as some demonstrations descended into violence.
But in London the attention fast turned to the apparent defiance of social distancing rules, sparking a backlash online.
The city's mayor Sadiq Khan tweeted: "Lockdown has not been lifted. The virus is still out there," reminding people to keep their distance.
Another Twitter user said: "A second wave is coming without a doubt," adding the action showed a "reckless disregard" for the social distancing rules.
Another user wrote: "If there's a spike in the virus again over the next few weeks, I'll not be staying at home again under strict lockdown."
One posted a picture of the protests in London, adding: "Welcome to the UK, with the highest death toll for #coronavirus in Europe! #SocialDistancinguk".
— Tyler Wakeford (@TylerWakeford99)May 31, 2020
But others hit back, accusing those criticising the protesters of double standards.
One user wrote: "Those hating on the BLM (Black Lives Matter) PROTESTS are the same ones that were flaunting the rules. Don’t try to turn this around."
Another fired back: "People have been flouting the rules for weeks and weeks, and it's now suddenly a problem when there are #BlackLivesMatter protests?"
— Rubydaly (@isaaccarlo3)May 31, 2020
Earlier on Sunday, Foreign Secretary Dominic Raab said video footage of Mr Floyd’s death was “very distressing”, but he would not comment on Donald Trump’s response to the widespread protests.
The president has been criticised after warning on Twitter that “looting leads to shooting”.
He later attempted to clarify his words by further tweeting on Friday: “Looting leads to shooting, and that’s why a man was shot and killed in Minneapolis on Wednesday night – or look at what just happened in Louisville with 7 people shot. I don’t want this to happen, and that’s what the expression put out last night means.”
Mr Raab told Sky’s Sophy Ridge on Sunday: “I’m not going to start commenting on the commentary or indeed the press statements that other world leaders make, or indeed the US president.
“What we do know is that the lead suspect has now been charged with murder, there is a federal review and we want to see de-escalation of all of those tensions and American come together.”