New Orleans, Louisiana - The FBI is probing the "terrorist" connection of the US Army veteran who drove his truck into New Year's Eve revelers, killing at least 15, according to the latest tally.

Shamsud-Din Jabbar, a 42-year-old US citizen from Texas, was identified as the main suspect in the horrific attack. 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."

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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 the explosion later on Wednesday of a Tesla Cybertruck outside a hotel owned by President-elect Donald Trump in Las Vegas that killed one person, though he cautioned that none had been found so far.

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

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 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, up from the 10 initially confirmed dead.

Police said the incident began around 3:15 AM, 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.

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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.

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 US, 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.