The crowd was led by several hundred neo-Nazis who were then joined by thousands of ordinary citizens, donning polo shirts and baggy chino shorts in various boring tones and while others threw off their attire to show off sagging tattoos or openly urinated in the streets, footage and photographs showed.
Khan said the counter-protests were clearly created to provoke violence, and the best way to respond was to stay home and ignore them.
London's Metropolitan Police had said those who had ignored the pleas not to protest must comply with conditions imposed, including keeping to separate designated areas and dispersing by 1600 GMT.
About 1,000 far-right activists took to London's streets, vowing to protect historic monuments that have been targeted on the fringes of recent Black Lives Matter marches.
"These people who are marching did not set out to do this, but a very, very small, extremely explosive group of people who have made a practice of hijacking entirely responsible demonstrations are behaving in an unspeakable and cowardly manner".
Anti-racism protesters, who have staged demonstrations since the death of African American George Floyd after a Minneapolis police officer knelt on his neck for almost nine minutes while detaining him on May 25, have put statues at the forefront of their challenge to Britain's imperialist past.
About two miles away, around 20 anti-racism protesters gathered at Hyde Park, holding Black Lives Matter placards, even though organisers had told them not to attend fearing clashes.
Earlier, a statue of slave trader Edward Colston was hauled from its plinth by protestors in the English port city of Bristol on Sunday and dumped in the harbour.
The statue of Churchill was completely boarded up this week in an effort to protect it from vandals.
British Prime Minister Boris Johnson condemned the clashes as "racist thuggery". Authorities also fenced off the nearby Cenotaph, a memorial to Britain's war dead.
Tomorrow's major Black Lives Matter rally in central London has been cancelled after concerns of clashes with far-right groups who have urged people to head to their local war memorial and statues tomorrow to form a protective cordon.
Police Commander Bas Javid urged people not to gather in large groups at all because of the coronavirus.
The protests were meant to wind down by 5 p.m. BST, but it does not appear that all protesters or activists have complied.
"As for the planned demonstrations, we all understand the legitimate feelings of outrage at what happened in Minnesota and the legitimate desire to protest against discrimination".
Dozens were arrested last weekend, and a police horse was pictured bolting past the crowds amid the chaos.
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