Demonstrators then marched to the US embassy, where a long line of officers surrounded the building. Several hundred sat in the street and waved placards
Thousands of people protested in London and Berlin on Sunday in solidarity with protesters in the United States demonstrating against the death of George Floyd, who was killed by a white policeman kneeling on his knee at Minneapolis.
Chanting "no justice, no peace", and waving placards with the words "How many more?" at Trafalgar Square, the protesters ignored UK government rules banning crowds because of the coronavirus pandemic. Police did not stop them either, reports Al Jazeera.
Demonstrators then marched to the US embassy, where a long line of officers surrounded the building. Several hundred sat in the street and waved placards.
US embassy in Berlin also witnessed protest from several hundred people who staged a rally outside and held up posters saying "Justice for George Floyd", "Stop killing us" and "Who's next".
Al Jazeera's correspondent in London Nadim Baba said protests in support of US demonstrators also took place in Manchester in the northwest of England.
"One of the chants that was popular was 'no justice, no peace', which is not a new chant in Britain," said Baba, comparing the demonstrations to the 2011 London riots which were sparked by the death of a Black man named Mark Duggan during a police operation.
"That alerted people to the issue of discontent within the Black population and also [served as] a reminder about the consistent death of Black men in police custody over the past few decades," he added.
Floyd's death after his arrest in Minneapolis, Minnesota, on Monday has triggered a tide of protests in the US.
Demonstrations against racism and police brutality spread to many cities across the US as people in many parts of the country defied curfews to protest against the killing of Floyd.
The days-long protests sweeping the nation have reawakened outrage over years of deaths of Black people at the hands of police, renewing long-standing accusations of institutionalised and systemic racism.
Some rallies have turned violent as demonstrators blocked traffic, set fires and clashed with riot police, some of whom fired tear gas and plastic bullets in an effort to restore order.