At least four dead, dozens injured in Alabama shooting

At least four people have been killed and dozens more injured in a mass shooting in one of the most popular entertainment areas of Birmingham, Alabama.

The shooting erupted just after 11pm Saturday local time (4pm Sunday NZT) in the Five Points South area.

CNN reported that two men and a woman were pronounced dead at the scene, while a fourth victim died in hospital later.

"Multiple shooters fired multiple shots on a group of people," Birmingham police officer Truman Fitzgerald told CNN.

No suspects were yet in custody.

The victims were all shot on the streets or footpaths, Fitzgerald told CNN.

Detectives were trying to determine whether the shooters were on foot or in a vehicle.

Further gunshot victims were found in the area, while other victims arrived at local hospitals, Fitzgerald told CNN.

"We have dozens of gunshot victims from this area. I'm told at least four of those gunshot victims are life-threatening, the others have various injuries."

It was unclear exactly how many people opened fire or the motivation behind the attack, Fitzgerald said.

The Independent reported that police were looking into whether a 'switch' - a device allowing a gun to act as an automatic weapon - had been used in the incident.

They had asked the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives to help with the investigation.

Police were calling for any witnesses to come forward, the Independent reported.

"There is no greater resource than the public," the media outlet reported Fitzgerald as saying.

"We will do everything we possibly can to make sure we uncover, identify and hunt down whoever is responsible for preying on our people."

According to the Gun Violence Archive, there have been at least 403 mass shootings across the United States this year.

A mass shooting is defined as a shooting that kills or wounds at least four victims.