JERSEY CITY, N.J. -- The gunmen in a furious firefight that left six people dead in Jersey City clearly targeted a Jewish market, the mayor said Wednesday, fueling growing suspicions the bloodshed was an anti-Semitic attack.

Mayor Steven Fulop refused to call it an anti-Semitic attack but said surveillance video showed the gunmen driving slowly through the city's streets and then stopping outside a kosher grocery store, where they calmly got out of their van and immediately opened fire.

Neither the state attorney general, who is running the investigation, nor any other law enforcement authority has confirmed the shooters targeted Jews. City Public Safety Director James Shea said Tuesday there was no indication it was terrorism. And police released no immediate information on the killers.

A police officer, three bystanders and the killers all died in the violence Tuesday afternoon in the city of 270,000 people across the Hudson River from New York City.

The shooting began near a cemetery, where Detective Joseph Seals, a 40-year-old member of a unit devoted to taking illegal guns off the street, was killed while trying to stop "bad guys," Police Chief Michael Kelly said without elaborating.

The killers then drove a stolen rental van over a mile to the kosher market, where they used high-powered rifle fire in a drawn-out battle with police that filled the streets with the sound of heavy gunfire and turned the city into what looked like a war zone, with SWAT officers in full tactical gear swarming the neighbourhood.

At the grocery store, police found five bodies -- the killers and three people who apparently happened to be there at the time. Police said they were confident the bystanders were shot by the gunmen and not by police.

Fulop said a review of security camera footage has led to the conclusion that the gunmen targeted the market.

"Last night after extensive review of our CCTV system it has now become clear from the cameras that these two individuals targeted the Kosher grocery location," Fulop tweeted.

At a later news conference, Fulop said the surveillance video shows the van driven moving slowly and then stopping in front of the grocery store.

"There were multiple other people on the street so there were many other targets available to them that they bypassed to attack that place, so it was clear that was their target and they intended to harm people inside," he said.

But Fulop cautioned: "I didn't use the word `anti-Semitic.' Anything else is open for investigation."

Jewish leaders and the Anti-Defamation League, which tracks anti-Semitic attacks, expressed concern about the deaths.

New York Mayor Bill de Blasio said on MSNBC that the attack was "clearly a hate crime," while New York Gov. Andrew Cuomo pronounced it a "deliberate attack on the Jewish community." They announced tighter police protection of synagogues and other Jewish establishments in New York as a precaution.

In the deadliest attack on Jews in U.S. history, 11 people were killed in an October 2018 shooting at a synagogue in Pittsburgh. Last April, a gunman opened fire at a synagogue north of San Diego, killing a woman and wounding a rabbi and two others.

The kosher grocery is a central fixture in a growing community of Orthodox Jews who have been moving to Jersey City in recent years and settling in what was a mostly black section of Jersey City.

Chabad Rabbi Moshe Schapiro, who shops at the store and attends a synagogue next door, said he spoke with the store owner, Moishe Ferencz.

"He told me he had just walked out of the store into the synagogue not five feet away just before this happened, and then he couldn't get back for hours," Schapiro said. "His wife was inside the store. He said, `I hope my wife is safe."'

The names of the victims inside the store were not immediately released, pending notification of relatives.

Police also removed what they described as a possible "incendiary device" from the van.

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This story has been corrected to show that the spelling of the name of the rabbi who attends a synagogue next to the market is Moshe Schapiro, not Moshe Shapiro.

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Associated Press writers Wayne Parry in Atlantic City; Deepti Hajela in Jersey City, Michael Catalini in Trenton, Claudia Lauer in Philadelphia and Michael Sisak and Shelley Acoca in New York contributed to this story.