Protesters returned to Baltimore’s streets today to vent their outrage over the death of an African-American man from injuries he apparently sustained when he taken into custody two weekends ago.

Organisers anticipated the biggest outpouring of public anger since Freddie Gray, 25, was arrested on April 12, only to die in a coma seven days later from severe spinal injuries.

Some 200 to 300 protesters set off in the early afternoon from the west Baltimore housing project where Gray was apprehended, heading toward the district police station that has been the focal point of nightly demonstrations this week.

"No justice, no peace!" chanted the crowd, under a forest of banners, including one featuring portraits of 50-odd African-Americans who have died in confrontations with police officers in recent years.

More protesters were expected later for a major rally outside City Hall, called by Black Lawyers for Justice and other groups.

Tensions are simmering in the blue-collar Mid-Atlantic port city of 620,000 as investigators try to establish the circumstances that led to Gray’s death.

In a press conference Friday, top officials acknowledged Gray should have gotten medical help at the moment he was detained, when he was seen by bystanders — and caught on video — howling in pain.

They also revealed that Gray — contrary to policy — was not buckled into his seat in the van, which made at least three unexplained stops on its way to the Western District police station.

Gray died tomorrow with 80 per cent of his spine severed at the neck, lawyers for his family have said. His funeral is scheduled for Monday.

Six officers have been suspended with pay as the police investigation inches closer to a May 1 deadline to submit findings to a Maryland state prosecutor, who could decide to press charges.

Gray’s death is the latest in a string of high-profile confrontations — including the fatal shooting of unarmed teenager Michael Brown in August — that have stoked a national debate about police conduct toward black men and boys in the United States.