UPDATE: 1:50 p.m.

A police officer and multiple other people were killed in a furious gunbattle Tuesday that filled the streets of Jersey City with the sound of heavy gunfire for about an hour, authorities said.

Authorities said they believe the shootout was not an act of terrorism, but the bloodshed was still under investigation.

Officials gave no immediate details on what set off the shooting and how it unfolded, and there was no word on how many suspects were involved or whether anyone had been taken into custody.

One officer was pronounced dead at a hospital, and multiple other people were found dead at a kosher supermarket, Mayor Steven Fulop said without specifying how many were killed. A second officer was struck in the shoulder by gunfire, and two others were hit by shrapnel, Fulop said.

The shooting spread fear through the neighbourhood, and the nearby Sacred Heart School was put on lockdown as a precaution.

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 cellphones, some whooping when bursts of gunfire could be heard.

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!”

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UPDATE: 1 p.m.

Authorities now say that multiple people are dead after a shooting in Jersey City on Tuesday.

They said there was no indication terrorism was behind the standoff marked by heavy gunfire.

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UPDATE: 12:40 p.m.

Prosecutors say that one police officer has been killed and two more and a civilian wounded in the standoff in Jersey City.

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UPDATE: 12:20 p.m.

Police officers were shot Tuesday in a standoff marked by heavy gunfire reverberating through a Jersey City neighbourhood, authorities said.

The nearby Sacred Heart School was put on lockdown, but all staff and students were safe, according to a statement from the Archdiocese of Newark.

Sporadic, heavy gunfire rang out over the course of at least an hour along a major thoroughfare but has quieted down. SWAT teams, state police and federal agents responded to the scene, and police blocked off the area, which, in addition to the school, has some stores, a kosher supermarket and a hair stylist.

FBI spokeswoman Patty Hartman said that more than one officer has been shot but could not give any other information.

“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," Democratic Gov. Phil Murphy said. “I have every confidence in our law enforcement professionals to ensure the safety of the community and resolve this situation.”

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ORIGINAL: 11:30 a.m.

Sporadic, heavy gunfire rang out Tuesday over the course of at least an hour in a Jersey City neighbourhood.

It was not yet clear if anyone was injured.

SWAT teams and federal agents responded to the scene, and police blocked off the major thoroughfare where the shooting occurred. The area has a Catholic school, some stores, a kosher supermarket and a hair stylist. Phones rang unanswered at several businesses. The Catholic parish, Sacred Heart, has closed, and no one answered at its associated school, which runs from preschool through eighth grade.

Police tactical teams were going through the school, which remained on lockdown, according to scanner traffic.

Jersey City Police said they had no information to provide over the phone on the shooting.

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

Loud volleys of gunfire could be heard at regular intervals but subsided around 2 p.m. in the city, which is just across the Hudson River from Manhattan.

Video images show a line of police officers armed with weapons pointed in several directions walking down the sidewalk. The Bureau of Alcohol, Tobacco, Firearms and Explosives said it was responding.

Dozens of bystanders pressed against the police barrier to film the action on cellphones, some whooping when gunfire bursts filled the air.

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

“I can hear the gunshots. It's like firecrackers going off. They were shooting like crazy about an hour ago. Then it stopped for like 20 or 30 minutes. The cops were clearing everyone off the streets,” said Patel.