A shooting at a backyard barbecue in the northeastern US state of Pennsylvania has left five people dead, and at least two suspects are still on the run, police said yesterday.

Four of the victims -- three women and one man -- died at the scene while another woman succumbed to her wounds in hospital, police said in a statement.

Two men are in critical condition and a woman is in stable condition following the incident that unfolded at a home late Wednesday in the town of Wilkinsburg, they said.

"The ballistic evidence on the scene leads police to believe that two different weapons were discharged from two different people," the statement said.

No one has been taken into custody and police were urging witnesses to come forward to aid their investigation, which they said was still in its preliminary stage.

Police said shots were fired from an alley and that when partygoers tried to seek cover in the home, someone on the side or backyard adjacent to the residence fired at the back porch, where all four deaths occurred.

The rampage represents the latest mass shooting to rock the United States, where such attacks have become commonplace. Gun violence is responsible for some 30,000 deaths per year in the country, with 330 mass shooting incidents recorded last year.