Teenager killed as driver ploughs into pedestrians at New York's Times Square.

A former US Navy veteran who appeared intoxicated has driven his car the wrong way up a Times Square and ploughed into pedestrians on the footpath, killing a teenager and injuring 22 other people, authorities and witnesses said.

The 18-year-old pronounced dead was named as Michigan tourist Alyssa Elsman, the NY Post reports. Her 13-year-old sister was among the injured.

The driver, Richard Rojas, a 26-year-old Bronx resident, was taken into custody and is being tested for alcohol. The New York Police Department is not treating the incident as terror-related.

Pandemonium erupted when the vehicle barrelled through the tourist hub on Thursday afternoon local time and came to rest with two of its wheels in the air.

The car leaned on a lamppost and steel barriers intended to block vehicles from getting onto the sidewalk.

"He's just mowing down people," said Asa Lowe, of Brooklyn, who was standing outside a store when he heard screaming. "He didn't stop. He just kept going."

The crash happened midday on a hot, clear day that brought large crowds of people into the streets to enjoy the good weather. Video posted online showed steam or smoke pouring from the car for a few moments after it stopped moving.

After the car struck a barricade and stopped, the driver climbed out of his vehicle, Lowe said.

"He just started running until people tackled him down," Lowe said. "Citizens just reacted."

Rojas had been arrested at least twice previously for driving while intoxicated, once in 2008 and once in 2015, police said.

He was in custody, and it wasn't clear if he had an attorney yet who could comment on his behalf.

Police do not suspect a link to terrorism, but the vehicle was checked by the bomb squad and certain city landmarks were getting a beefed-up police presence.

Police said Rojas made a quick U-turn onto 42nd Street and then drove up the footpath for three blocks, passing tourist draws like the Hard Rock Cafe and the Bubba Gump Shrimp Company restaurant and mowing people down before slamming into a pole. He was combative with officers arresting him, authorities said.

Student Bruno Carvalho said the car approached quickly and passed him on the footpath.

"People just got stunned," he said. "I don't think there was actually time for screaming."

He said he saw about five people who looked gravely injured - "people, really bad, in front of us."

The White House said President Donald Trump was informed of the situation in Times Square and would continue to be briefed as it unfolded.