The New York terror suspect fled his truck after ramming into a school bus with children on board, according to the NYPD commissioner James P O'Neill.

The 29-year-old suspect drove the rental truck down a busy cycle path near the World Trade Center - hitting cyclists and pedestrians - before crashing into the bus belonging to nearby Stuyvesant High School.

The school said two adults and two children inside the bus “might be a little hurt, but no one is dead.”

After crashing, the driver exited the vehicle holding what later turned out to be imitation firearms, and was shot by police in the stomach. He is now in custody and is being treated in hospital.

A teenage student from the high school told the New York Post: "He came out of one of the cars. He had two guns. He was running around Chambers (Street) and somebody started to chase him. I heard four to six gunshots - everybody starts running."

The aftermath of the New York truck attack (AFP/Getty Images)

It has been reported that the 29-year-old suspect screamed "Allahu Akbar" after the crash.

Six people were declared dead at the scene and two were pronounced dead later at hospital.

Eleven people have been left with serious injuries, but New York police commissioner James O'Neill "there may be more".

The situation unfolded just after 3pm when the southbound truck veered onto a bike path on West Street near Houston Street.

“He entered the bike bath at Houston Street and exited the bike path when he collided with the bus at Chambers street,” O’Neill said.

New York Truck attack Show all 6 1 /6 New York Truck attack New York Truck attack Investigators inspect the truck following the attack Investigators inspect a truck following a shooting incident in New York on 31 October 2017. Several people were killed and numerous others injured in New York on Tuesday when a suspect plowed a vehicle into a bike and pedestrian path in Lower Manhattan, and struck another vehicle on Halloween, police said. A suspect exited the vehicle holding up fake guns, before being shot by police and taken into custody, officers said. The motive was not immediately apparent. Getty New York Truck attack A paramedic looks at a body along the bike path A paramedic looks at a body covered under a white sheet along the bike path 31 October 2017, in New York. A motorist drove onto a busy bicycle path near the World Trade Center memorial and struck several people Tuesday, police and witnesses said. AP Photo/Bebeto Matthews New York Truck attack The truck driver collided with a school bus Authorities respond near a damaged school bus Tuesday, 31 October 2017, in New York. A motorist drove onto a busy bicycle path near the World Trade Center memorial and struck several people, police and witnesses said. Two adults and two children were on the bus at the time. AP Photo/Bebeto Matthews New York Truck attack A young girl reacts to the scene A young girl reacts as police officers secure an area following a shooting incident in New York on 31 October 2017. Several people were killed and numerous others injured in New York on Tuesday after a vehicle plowed into a pedestrian and bike path in Lower Manhattan, police said. 'The vehicle struck multiple people on the path,' police tweeted. 'The vehicle continued south striking another vehicle. The suspect exited the vehicle displaying imitation firearms & was shot by NYPD.' DON EMMERT/AFP/Getty Images New York Truck attack Police officers arrive at the scene Police officers arrive at the scene following a shooting incident in New York on 31 October 2017. Multiple people were hurt in downtown Manhattan, US media reported after police confirmed that they were responding to reports of a shooting. Police said they had mobilized to the scene in Lower Manhattan and that one person was in custody, giving no further details. DON EMMERT/AFP/Getty Images New York Truck attack Emergency personnel respond to truck attack in lower Manhattan Emergency personal respond after reports of multiple people hit by a truck after it plowed through a bike path in lower Manhattan on 31 October 2017 in New York City. According to reports up to six people may have been killed. Kena Betancur/Getty Images

New York Governor Andrew Cuomo called it a “lone wolf” attack and said there was no evidence to suggest it was part of a wider plot.