Police arrested 23 people after a protest in London over the death of African-American George Floyd.
Thousands marched across London on Sunday to demonstrate against his death last Monday in the US city of Minneapolis.
A white ex-police officer has been charged with murdering Mr Floyd, 46.
Derek Chauvin, 44, who has since been dismissed from the police department, is accused of pressing his knee to Mr Floyd’s neck for eight minutes and 46 seconds.
In a video of the incident, Mr Floyd can be heard saying, “don’t kill me” and “I can’t breathe”.
The protest in London was organised by the Black Lives Matter movement and started in Trafalgar Square, where people chanted Mr Floyd's name and knelt on the floor en masse, before heading to the US embassy in Battersea.
Hundreds of people also took part in protests in Cardiff and Manchester.
The Metropolitan Police said 23 people had been arrested as a result of the protest in London.
After Battersea, protesters – many wearing masks – crossed the River Thames again, and headed through affluent Chelsea, Knightsbridge and Notting Hill, before gathering at the base of Grenfell Tower, where 72 people died in a fire in 2017.
The Metropolitan Police said the arrests varied in suspected offences, from possession of an offensive weapon to assault on police, obstructing a public carriageway and breaches of COVID-19 legislation.
In the US, tens of thousands of protesters took to the streets in another night of protests.
City and state officials deployed thousands of National Guard soldiers, enacted strict curfews and shut down transport systems to slow protesters' movements, but that did little to stop parts of many cities from again erupting into violence.
Protesters in Philadelphia threw rocks and Molotov cocktails at police, officials said, while thieves in more than 20 California cities smashed their way into businesses and ran off with as much as they could carry – boxes of trainers, armloads of clothes, and mobile phones, TVs and other electronics.
Police fired tear gas and stun grenades into a crowd of more than 1,000 protesters across the street from the White House in Washington DC.
It emerged that US president Donald Trump was rushed to a White House bunker by Secret Service agents on Friday during a previous night’s demonstrations. Trump spent nearly an hour in the bunker.
At least 4,400 people have been arrested over days of protests in the US.