WASHINGTON - President Trump on Tuesday suggested without evidence that a 75-year-old man who was knocked to the ground by police in Buffalo, N.Y., last week during a protest over George Floyd's death was a member of antifa and that the incident was "a set up."

Video taken Thursday shows two officers pushing the man, Martin Gugino, who then falls and hits the back of his head on the pavement, causing him to bleed. Police initially claimed Gugino tripped. He remained hospitalised in serious but stable condition Monday.

In his tweet, the president tagged the far-right One America News Network.

"Buffalo protester shoved by Police could be an ANTIFA provocateur," Trump tweeted to his 81.9 million Twitter followers. "75 year old Martin Gugino was pushed away after appearing to scan police communications in order to black out the equipment. @OANN I watched, he fell harder than was pushed. Was aiming scanner. Could be a set up?"

Trump's suggestion echoed conspiracy theories circulating on fringe corners of the internet and on OANN, which claimed on air that "the latest tensions in the Buffalo police department could be the result of a false flag provocation by far left group antifa."

The officers, Robert McCabe and Aaron Torgalski, were initially suspended without pay, prompting dozens of fellow officers to step down from Buffalo's Emergency Response Team unit in protest.

McCabe and Torgalski were later arrested and charged with second-degree assault. They were released without bail.

New York Gov. Andrew Cuomo called the situation "horrendous" and said there was no need to use force.

"I think there was criminal liability from what I saw on the video," Cuomo said. "I think what the mayor did and the district attorney did was right, and I applaud them for acting as quickly as they did."

"There's no tolerance for delaying justice in society anymore," Cuomo added. "Justice delayed is justice denied."

Trump is known to promote baseless conspiracies from his Twitter perch.

The president recently drew fierce blowback after he repeatedly suggested without evidence that MSNBC host Joe Scarborough should be investigated in the death of a young woman who died after falling in his congressional office almost two decades ago. A medical examiner ruled her death an accident, concluding she had an undiagnosed heart condition.