Shocking footage has emerged of police in upstate New York shoving a white-haired man to the ground and appearing to march past him as he lay bleeding on the ground.

The video – shot by a journalist from public radio station WBFO in Buffalo and posted online – comes as protests continue across the US at the death at the hands of police of George Floyd in Minneapolis on May 25.

In the footage, the 75-year-old man approaches a line of officers clad in riot gear.

Warning: Graphic footage

One officer pushes him with a baton and a second one pushes him with his hand. The sound of a crack is heard and then blood is seen trickling from the man’s head.

The video shows the majority of the officers march past the fallen man. The officer who shoved him with the baton starts to lean over him before he is motioned away by another officer. Someone is heard calling for a medic.

The radio station reported that medics helped the man into an ambulance.

A Buffalo Police spokesman initially said one person had been injured when he tripped and fell during a skirmish between police and protesters.

Only hours later, Buffalo Mayor Byron Brown issued a statement saying he was “deeply disturbed by the video”, according to WBFO.

“After days of peaceful protests and several meetings between myself, police leadership and members of the community, tonight’s event is disheartening,” he said.

The two officers involved have since been suspended without pay, and an internal affairs investigation is underway.

The injured man, whose name has not been released, is in stable condition at a Buffalo hospital.

Elsewhere, park police in Maryland are looking for a man after another video posted to social media appeared to show him violently grab an object from a child who was posting signs protesting the death of George Floyd.

Tweet from @VicStoddard

Police tweeted the assault occurred on Monday on the Capital Crescent Trail, a 12-kilometre rail trail that runs from suburban Washington into Maryland.

In the 34-second video, the cyclist walks away from one woman whose right arm is extended towards the man.

The cyclist then turns toward what appears to be a young girl.

The unidentified cyclist was then shown picking up his bicycle, running with it toward the person shooting the video and forcing that person to the ground.

The two incidents are the latest in a string of violent confrontations in 10 days of unrest across the US following Mr Floyd’s death.

A memorial service was held for Mr Floyd in Minneapolis on Thursday (local time).

Prominent civil rights activist the Reverend Al Sharpton, who delivered a eulogy, told mourners Mr Floyd’s fatal encounter with police and the nationwide protests his death ignited has marked a reckoning for America over race and justice, demanding, “Get your knee off our necks.”

Reverend Sharpton said Mr Floyd’s fate – dying at the hands of police, pinned to the ground under the knee of a white officer – symbolised a universal experience of African-Americans.

“George Floyd should not be among the deceased. He did not die of common health conditions. He died of a common American criminal justice malfunction,” Reverend Sharpton said. “It’s time for us to stand up in George’s name and say, ‘Get your knee off our necks.'”

He led mourners in eight minutes and 46 seconds of silence, the length of time Mr Floyd lay on a Minneapolis street with a knee pressed into his neck.

The service, which drew comic actors Kevin Hart and Tiffany Haddish as well as US senator Amy Klobuchar of Minnesota, coincided with a separate tribute to Mr Floyd in the New York City borough of Brooklyn, a major flashpoint of protests in recent days.

The services capped nine nights of street demonstrations in Mr Floyd’s name across the US – punctuated by sporadic arson, looting and clashes between protesters and police.

The rage appeared to ebb on Wednesday, after prosecutors in Minneapolis elevated murder charges against one police officer jailed last week in Mr Floyd’s death and arrested three others accused of aiding and abetting the first.

The four sacked officers each faces a maximum sentence of 40 years in prison if convicted of the most serious charges against them.

On Thursday, US Attorney-General William Barr said evidence had surfaced of foreign interests and “extremist agitators” affiliated with left-wing movements infiltrating the protests to foment unrest, though he offered no details.

Services for Mr Floyd are expected to stretch across six days and three states, including memorials in North Carolina and Houston. A funeral was planned for Tuesday.

-with AAP