Four people have died and more than 20 were wounded during a shooting in a nightlife area in Birmingham, Alabama, according to police and news reports.

Dozens of people were shot on 20th Street near Magnolia Avenue in the Five Points South area, the Birmingham Police Department said in a social media post.

Birmingham Police Department Officer Truman Fitzgerald said the shooting, which saw at least 21 people wounded, happened shortly after 11pm local time in the 2000 block of Magnolia Avenue South.

"We believe that multiple shooters fired multiple shots on a group of people," Mr Fitzgerald told local media.

He said there were "dozens of gunshot victims" and at least four had "life-threatening" injuries.

The Birmingham Fire and Rescue Service pronounced three people dead on the scene and a fourth person was pronounced dead at University of Alabama at Birmingham Hospital.

Police said the victims found dead at the scene included two men and a woman.

Other victims were transported to hospitals in private vehicles, police told WBMA.

Police said there were no immediate arrests.

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

The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives are also investigating the incident.

This year, there have been at least 403 mass shootings — defined as a shooting involving at least four victims, dead or wounded — across the United States, according to the Gun Violence Archive.

AP/AFP