Members of the Bloods and Crips gang members have denied police claims that they called for police to be killed in the wake of the death of black man Freddie Gray in police custody.

The gangs claimed that they were being falsely blamed for promoting violence, but had in fact come together to help unite the community.

On Monday, police issued a nationwide alert, warning that Bloods, Crips and members of the Black Guerrilla Family had united to "take out" police officers in the wake of Gray's death.

Gang members rejected the claim.

"We want to tell the people of Baltimore city that the image they're trying to portray of gangs in Baltimore, of the BGF, the Bloods, Crips, we did not make a truce to harm cops. We did not come together against the cops. We're not about to let ya'll paint that picture of us," a Bloods member told WBAL.

A picture taken of Bloods, Crips and Nation of Islam Members together at a peaceful protest in Baltimore on Saturday was evidence of a violent pact between the gangs, some Twitter users claimed.

Nation of Islam members told the Daily Beast though that they had brokered the truce in honour of Gray.

In an interview with the Baltimore Sun men claiming to be from the rival gangs called for an end to the riots.

"We not here for nobody to get hurt," a man who gave his name as Charles said. "We don't want nobody to get hurt. All that about the police getting hurt by certain gangs, that's false. We not here for that. We here to protect our community, and that's it. We don't want no trouble. We're doing this because we don't want trouble."

The two gangs emerged in LA in the late 1960s, and thousands are believed to have been killed as the groups waged war with one another across the city.

Both gangs have spread throughout the US, and have tens of thousands of members nationwide arranged into loosely allied smaller groups or sets.

The two gangs have allegedly put aside their rivalries before to promote community cohesion, with the MadameNoire web publication reporting in August that Bloods and Crips members holding up signs in Ferguson, Missouri, were unarmed black man Michael Brown was shot dead by a police officer, saying "NO MORE CRIPS. NO MORE BLOODS. ONE PEOPLE. NO GANG ZONE."