The suspect, described by one city leader as being in "full military gear," died after a shootout with police, law enforcement officials said.
"This man was trying to run over as many people as he could," police chief Anne Kirkpatrick said at a press conference on Wednesday.
"He was hell-bent on creating the carnage and the damage that he did."
The incident occurred about 3.15am at the intersection of Canal and Bourbon Streets - a historical tourist destination in the city's French Quarter known for attracting large crowds with its music and bars - during New Year's Eve celebrations, the city said in a statement.
Police chief Anne Kirkpatrick says a suspect was "trying to run over as many people as he could". (AP PHOTO)
Kirkpatrick said the driver, who swerved around barricades, fired at police and struck two police officers from the vehicle after it crashed.
The officers were in stable condition, she added.
"We know the perpetrator has been killed," New Orleans City Councilman Oliver Thomas said.
"As we search for a motive, remember there is no making sense of evil."
There was no immediate word on the driver's identity.
More than 300 officers were on duty at the time of the incident, police said.
At a news conference, New Orleans Mayor LaToya Cantrell described the killings as a "terrorist attack" but an assistant FBI agent in charge initially said it was "not a terrorist event".
The FBI said in a statement on Wednesday it was investigating the incident as an act of terrorism.
An assistant FBI agent said a suspected improvised explosive device was found but provided no further details.
"From what I understand, there is a potential that other suspects could be involved in this, and all hands on deck on determining who these individuals are and finding them," New Orleans City Council [resident Helena Moreno told 4WWLTV.
"Information that I received is that this individual was in full military gear, that he is apparently not local, and that he was prepared, and that he was very prepared to inflict horrific pain on the people on Bourbon Street," Moreno said.
Authorities say a driver fired at police and struck two police officers after his truck crashed. (AP PHOTO)
"A horrific act of violence took place on Bourbon Street earlier this morning," Louisiana Governor Jeff Landry said on X, urging people to stay away from the area where the attack took place.
A couple told CBS News that they heard crashing noises coming from down the street and then saw a white truck slam through a barricade "at a high rate of speed".
Zion Parsons, 18, told NOLA.com that he and his two friends were leaving a Bourbon Street eatery when they heard a commotion and saw a white car barrelling toward them.
He said he dodged the vehicle but one of his friends was struck, with her leg "twisted and contorted above and around her back".
"You can just look and see bodies, just bodies of people, just bleeding, broken bones," he said.
US President Joe Biden called the city's mayor to offer full federal support, the White House said in a statement.
Biden said the FBI was investigating the "horrific incident" as "an act of terrorism" and that he has directed his team to ensure every resource is available as authorities work to "get to the bottom of what happened as quickly as possible".
US Attorney General Merrick Garland said the "country woke up this morning to news of a terrible tragedy in New Orleans".
He said federal law enforcement agencies would "deploy every available resource to conduct this investigation".
President-elect Donald Trump said in a statement that his incoming administration would "fully support the City of New Orleans as they investigate and recover from this act of pure evil!".
Last month in Germany, a 50-year-old man was charged with multiple counts of murder and attempted murder after police said he plowed a car through crowds at a Christmas market in Magdeburg, killing five people and injuring scores.
with Reuters
