A driver in a pickup truck who officials said was “hell-bent on carnage” sped through a crowd of pedestrians in New Orleans' bustling French Quarter district, killing 10 and injuring 30 revellers early on New Year's Day.

The attack occurred around 3.15 am along Bourbon Street, known worldwide as one of the largest destinations for New Year's Eve parties, and with crowds in the city ballooning in anticipation for the Sugar Bowl college football playoff game at the nearby Superdome later in the day.

At a news conference, New Orleans Mayor LaToya Cantrell described the killings as a “terrorist attack” and the city's police chief said the act was clearly intentional. But an assistant FBI agent in charge declared that is was "not a terrorist event.” The news conference ended before authorities could reconcile the two characterisations.

Alethea Duncan, an assistant special agent in charge of the FBI's New Orleans field office, said officials were investigating the discovery of at least one suspected improvised explosive device at the scene.

Police Commissioner Anne Kirkpatrick said police officers would work to ensure safety at the Sugar Bowl, indicating that the game would go on as scheduled.

“He was hell-bent on creating the carnage and the damage that he did,” Kirkpatrick said. “It was very intentional behaviour. This man was trying to run over as many people as he could."

Two police officers who were shot after the driver emerged from the truck are in stable condition, she said.

Officials did not immediately provide an update on the status of the driver, whether there was an ongoing threat to the public or offer a suspected motive in the fatal incident.

NOLA Ready, the city's emergency preparedness department, said the injured had been taken to five local hospitals.

The White House said President Joe Biden has been briefed.