US authorities were investigating Thursday after an army veteran with an Islamic State flag who was "hellbent" on carnage steered a pickup truck into a crowd of New Year's revelers in New Orleans, killing at least 15 people and wounding dozens.

The FBI identified the attacker as Shamsud-Din Jabbar, a 42-year-old US citizen from Texas. He appeared to have been a real estate agent working in Houston and had served as an IT specialist in the military.

Officials said they were searching for accomplices but gave few details.

Police Superintendent Anne Kirkpatrick described Jabbar as a "terrorist," and the FBI said "an ISIS flag was located in the vehicle," using another name for the Islamic State jihadist group.

"It was just scary, I cried my eyes out honestly," tourist Ethan Ayersman, 20, told AFP in New Orleans.

He was among the masses visiting the colorful southern US city for New Year's celebrations and said he had enjoyed popular Bourbon Street — where the deadly assault later unfolded — into the early hours.

Later on, Ayersman said his brother woke him up after hearing gunshots and a car speeding.

From the window of their nearby rental, they could see "some of the bodies that were being lined up," Ayersman said.

US President Joe Biden, describing the attack as "despicable," said Jabbar had posted videos online hours before "indicating that he was inspired by ISIS."

Biden also said that law enforcement agencies were probing any possible links between the attack and an explosion later on Wednesday of a Tesla Cybertruck outside a hotel owned by US President-elect Donald Trump in Las Vegas that killed one person, though he cautioned that none had been found so far.

Officials said Wednesday a manhunt was underway, with FBI agent Alethea Duncan warning that authorities "do not believe that Jabbar was solely responsible."

Hunting bad people down

Louisiana Governor Jeff Landry said, "We're hunting some bad people down."

The FBI said it was conducting search warrants in New Orleans "and other states." Earlier, the bureau's field office in Houston, Texas said it was conducting activity "related" to the New Orleans attack.

An FBI spokesman told AFP that 15 people had been killed in the attack, citing the New Orleans coroner's office.

Among the dead, Nikyra Cheyenne Dedeaux, 18, graduated from high school last year and was to begin a nursing program this month, US media reported.

Her mother Melissa Dedeaux told the news website Nola.com that her daughter had snuck out to New Orleans from Gulfport, Mississippi with her cousin and a friend to celebrate the new year.

Reggie Hunter, a 37-year-old warehouse manager and father of two from Baton Rouge, was also killed in the attack, the New York Times reported, citing a relative.

The newspaper also identified Tiger Bech, a former football player at Princeton University, among those killed.

Aiming for 'carnage'

Police said the incident began around 3:15 AM (0915 GMT) near Bourbon Street in the heart of the French Quarter, packed with people celebrating the start of 2025.

The suspect drove a white Ford F-150 electric pickup into a group of pedestrians, then exited and was killed in a shootout with police — two of whom were wounded. Two homemade bombs were found and neutralized, the FBI said.

"This man was trying to run over as many people as he possibly could," Kirkpatrick told reporters.

Driving at "very high speed" and in a "very intentional" manner," he was hellbent on creating the carnage and the damage that he did," Kirkpatrick said. 

The Pentagon said Jabbar had served in the Army as a human resources specialist and an IT specialist from 2007 to 2015, and then in the army reserve until 2020. 

He deployed to Afghanistan from February 2009 until January 2010, an army spokesperson said.

Biden said that "thus far, there's nothing" linking the New Orleans attack with the Las Vegas explosion, which police described as an "isolated" incident.

The vehicles in the two incidents were both rented through the popular car-sharing app Turo. The sheriff in Las Vegas said that was a "coincidence... that we have to continue to look in to."

A spokesperson for the app, used by millions of people in the United States, said they were working with law enforcement.

"We do not believe that either renter... had a criminal background that would have identified them as a security threat," the spokesperson told AFP.  

Horror in famous neighborhood

In the early hours of the year's first day, revelers were celebrating in the French Quarter, renowned for its bars, restaurants, jazz history and Mardi Gras parties.

Bystander Zion Parsons said the revelry turned into a scene of horror.

"There were bodies and blood and all the trash," he told CNN. "People were terrified, running, screaming."

Another witness, Jimmy Cothran, told ABC that the mayhem left "10 bodies — six clearly, graphically deceased," and others "yelling with no one around."

New Orleans is one of the most heavily visited destinations in the United States, and will host the Super Bowl next month. 

The attack came just hours before the city was due to put on the Sugar Bowl, a major college football game. It was delayed until Thursday.