Joe Biden attacks US President Donald Trump over the way he has handled protests in the wake of the death of African American man George Floyd, calling out the President for the use of tear gas and flash grenades against protesters.

Speaking in Philadelphia a city rocked by sometimes violent protests in recent days Mr Biden took aim at President Donald Trump's handling of the wave of demonstrations across the US over racism and police misconduct.

"This president today is part of the problem and accelerates it," Mr Biden said, adding that Mr Trump is "consumed with his blinding ego.".

Cities across the US have seen widespread protests since George Floyd, an African-American man, died at the hands of police in Minneapolis on May 25.

Mr Biden's criticism comes a day after Mr Trump threatened the nation's governors that he would deploy the military to states if they did not stamp out violent protests over police brutality in the wake of the George Floyd killing that have riled the nation.

"We need our leaders — myself included — to listen to those who felt their only means of being heard was to take to the street in protest," Ms Kelly said after President Donald Trump threatened to deploy the military.

A state trooper who was run over by a sports utility vehicle [SUV] that barrelled through a group of officers at a George Floyd demonstration in Buffalo, an upstate city in New York, broke his leg and shattered his pelvis, police said.

A second passenger was uninjured and taken into custody, police said.

Protests in US cities triggered by the killing of George Floyd has reminded many people of the institutionalised racism toward people of colour, and historic inequalities in access to health, education and jobs, the top United Nations human rights official said on Tuesday.

"In the United States, protests triggered by the killing of George Floyd are highlighting not only police violence against people of colour, but also inequalities in health, education, employment and endemic racial discrimination.".

At least five US police officers were hit by gunfire during violent protests over the May 25 death of Floyd in police custody, police and media said on Monday, hours after the President said he would deploy the military if unrest did not stop.

Workers began Monday night removing the top portion of the obelisk in pieces in Birmingham's Linn Park, about a day after protesters tried to remove it themselves during a protest over police brutality, including the death of George Floyd in Minneapolis.