LONDON (Reuters) – Heavyweight boxing world champion Anthony Joshua described racism as a “pandemic” while addressing protesters at a Black Lives Matter march in London on Saturday.

Joshua, one of Britain’s highest-profile sportsmen, joined a march through the streets of his home town of Watford before gathering in a park where he recited a poem written by a friend.

“The virus has been declared a pandemic,” Joshua said. “This is out of control. And I’m not talking about Covid-19. The virus I’m talking about is called racism.”

Marches and protests have been held all over the world in response to the killing of unarmed black man George Floyd by a police officer in the U.S. on May 25. Four officers involved have since been charged over the death.

The 30-year-old Joshua, whose world heavyweight title defence against Bulgarian Kubrat Pulev scheduled for this month at Tottenham Hotspur’s stadium was postponed because of the COVID-19 pandemic, was dressed in all black for the event.

“We can no longer sit back and remain silent on these senseless, unlawful killings and sly racism on another human being – based on what? Only their skin colour,” the IBF, WBA and WBO world champion, who was using crutches and wearing a knee brace, after injuring his knee during training this week, added.

“We need to speak out in peaceful demonstrations — just like today, so well done Watford.

“We must not use a demonstration for selfish motives and turn it into rioting and looting.”

A spokesman for Joshua said his knee injury would be further checked by doctors, but “there is no immediate concern”.

The Black Lives Matters protests went on in London despite Health Minister Matt Hancock urging people not to attend large gatherings because of the pandemic.

The Metropolitan Police also said on Friday that the protests could be unlawful because they would break social-distancing advice.

Crystal Palace soccer player Andros Townsend took to Twitter to question why the authorities were trying to stop the marches.

“I find it funny how people in power are using covid 19 to try and stop the #BlackLivesMatter protests in the UK… where was this same energy when there were thousands congregating around parks/beaches? Don’t hide behind the virus, say the real reason! #BlackLivesMatter,” he said.