One man's act of humanity in the midst of chaotic violence in London has spread around the world after photos of the moment went viral.

Black Lives Matter counter-protesters had faced off against far-right groups in London's Trafalgar Square after the right-wingers headed to the UK capital with the stated aim of protecting statues from vandalism.

A man, identified as far-right by members of the crowd, was lying injured on the ground and was rescued by members of an anti-racist protest group.

Reports suggest he had been attacked by other protesters before his rescuers stepped in.

The injured man was identified as a far-right protestor. Photo / Getty Images

Photos show an unidentified black man hoisting the injured man on to his shoulders and carrying him to safety, flanked by riot police.

The Black Lives Matter group had earlier called off a demonstration scheduled for Saturday, saying the presence of counter-protesters would make it unsafe.

Some protesters still gathered at Hyde Park to denounce racism while hundreds of far-right activists demonstrated, despite strict police restrictions and warnings to stay home to contain the coronavirus.

Many from the far-right camp gathered around a statue of wartime Prime Minister Winston Churchill and the Cenotaph war memorial, both boarded up to guard against vandalism.

Officials put protective panels around the monuments amid fears far-right activists would seek confrontations with anti-racism protesters under the guise of protecting statues.

Some activists threw bottles and cans at officers, while others tried to push through police barriers. Riot police on horses pushed the crowd back. The protesters, who appeared to be mostly white men, chanted "England" and sang the national anthem.

"I am extremely fed up with the way that the authorities have allowed two consecutive weekends of vandalism against our national monuments," Paul Golding, leader of the far-right group Britain First, told the Press Association.

Scotland Yard said five people were arrested for violent disorder, assault on police and possession of weapons or drugs. Six police officers suffered minor injuries.

A large crowd gathers as the man is carried away. Photo / Getty Images

Monuments around the world have become flash points in demonstrations against racism and police violence after the May 25 death of George Floyd, a black man who died in Minneapolis after a white police officer pressed a knee to his neck.

In Britain, the protests have triggered a national debate about the legacy of empire and its role in the slave trade. A statue of slave trader Edward Colston was hauled from its plinth by protesters in the city of Bristol on Sunday and dumped in the harbour. In London, Churchill's statue was daubed with the words "was a racist".

Prime Minister Boris Johnson tweeted on Friday that while Churchill "sometimes expressed opinions that were and are unacceptable to us today," he was a hero and "we cannot now try to edit or censor our past". Churchill, whose first term spanned 1940-45, has long been revered for his leadership during World War II.

-Additional reporting, AP