US law enforcement say they responded to an active shooter situation in New Jersey, one officer has been confirmed dead.

Six people, including a police officer and three bystanders, were killed in a gun battle on Tuesday that filled the streets of Jersey City, New Jersey, with the sound of heavy gunfire for hours, authorities said.

The dead included two suspects, Jersey City Police Chief Michael Kelly said.

The shooting took place at two scenes, starting at a cemetery, where the officer was shot, and continuing at a kosher supermarket, where five more bodies were found, Kelly said.

“Our officers were under fire for hours,” the chief said.

He would not say exactly what set off the shooting but that he believes the officer who was killed was trying to stop some “bad guys”.

City Public Safety Director James Shea said that authorities believe the bloodshed was not an act of terrorism but that it was still under investigation.

Two other officers were wounded but were later released from the hospital, authorities said.

New York City Police officers on the scene of a shooting in Jersey City, New Jersey [Seth Wenig/AP photo]

‘Clear the street’

The bullets started flying early in the afternoon in the city of about 270,000 people, situated across the Hudson River from the Statue of Liberty.

SWAT teams, state police and federal agents converged on the scene, and police blocked off the area, which in addition to the school and supermarket included a hair salon and other shops. Dozens of bystanders pressed against the police barrier to capture the action on their mobile phones.

Video shot by residents recorded loud volleys of gunfire reverberating along one of the city’s main streets and showed a long line of law enforcement officers pointing guns as they advanced, yelling to bystanders, “Clear the street! Get out of the way!”

In a tweet, Governor Phil Murphy said that residents, among them children from the Sacred Heart elementary school were placed on lockdown during the incident.

All staff and students were safe, according to a statement by the Archdiocese of Newark.

“Our thoughts and prayers are with the men and women of the Jersey City Police Department, especially with the officers shot during the standoff, and with the residents and schoolchildren currently under lockdown,” Murphy tweeted.

I have been briefed on the unfolding situation in Jersey City. Our thoughts and prayers are with the men and women of the Jersey City Police Department, especially with the officers shot during this standoff, and with the residents and schoolchildren currently under lockdown. — Governor Phil Murphy (@GovMurphy) December 10, 2019

White House spokesman Hogan Gidley said President Donald Trump had been briefed on the shooting and was monitoring it.

Trump on Twitter called the shooting “horrfic”, adding that his “thoughts & prayers are w/ the victimes & their families”.

Law enforcement officers at the scene of shooting in Jersey City, New Jersey [Eduardo Munoz Alvarez/AP photo]

Andy Patel, who works at a liquor store about three blocks away from the site of the shooting, said there had been consistent gunfire fire for about an hour on Tuesday afternoon.

“It’s like firecrackers going off. They were shooting like crazy … The cops were clearing everyone off the streets,” Patel told the Associated Press.