A child is among those fighting for life, after two gunmen opened fire at an all-night music festival in New Jersey.

Twenty-two people were injured in the gunfire and resulting stampede.

Seventeen were hospitalised for gunshot wounds, and four -- including a 13-year-old boy -- remain in a critical condition.

One of the suspects was killed in the incident, while another suspect is in police custody.

Authorities say the shooting was due to a "neighbourhood beef".