The latest rallies in a fortnight of growing discontent took place as a New York prosecutor said he would impanel a grand jury to consider charges in one of the cases that has again brought to the fore the distrust felt by many African Americans towards the police.
Akai Gurley, 28, a father of a young daughter, was shot dead when a police officer opened fire in a dimly lit staircase at a Brooklyn apartment building as he walked with his friend late on November 20.
Brooklyn District Attorney Ken Thompson said he would present all the evidence for a grand jury to decide whether charges should be brought.
"It is important to get to the bottom of what happened," he said, giving no timetable for the jury to be appointed, nor for a decision to be reached.
"I pledge to conduct a full and fair investigation and to give the grand jury all of the information necessary to do its job. That information is still being gathered," Thompson said.
New York's police commissioner has said Gurley was a totally innocent victim and the family, who gathered for a private wake on Friday night ahead of the funeral on Saturday, has demanded justice.
Protesters hit the streets in recent days after grand juries declined to press charges against white officers responsible for the August 9 shooting death of unarmed 18-year-old Michael Brown in Ferguson, Missouri, and the July 17 chokehold death of black father-of-six Eric Garner in New York.
Several hundred protesters again staged rallies in New York on a rainy Friday night, one in Columbus Circle that moved to Fifth Avenue, and the second walking up Broadway from the south.
Similar protests were reported elsewhere across the United States including in Miami, Chicago, Boston, New Orleans and Washington, DC.
Dozens of protesters took to the streets of Washington D.C. on Friday in yet another day of demonstrations against police violence after grand juries in New York and Missouri decided not to indict police officers in the deaths of unarmed Black men.
The protesters gathered and staged a symbolic "die in", shouting "I can't breathe," a phrase Eric Garner shouted when he was placed in a chokehold by a New York police officer.
It was the first time the demonstrations demanding justice had taken to the streets in Miami, where protesters blocked traffic.
The decision last week in the Ferguson case sparked looting and arson in the St Louis suburb, while outrage over the Garner case has been the rallying cry for the latest protests.
On Thursday, demonstrators blocked roads, tunnels and bridges, and shouted "I can't breathe." Those were the final words gasped by Garner, a 43-year-old asthma sufferer, as police wrestled and held him to the ground in New York's State Island.