Newcastle Knights supporters have been injured by a car that crashed into a crowd gathered at a send-off for the grand final-bound team.

Three emergency services helicopters and 15 ambulances rushed to the scene, and several people were transported to John Hunter Hospital in various conditions.

The driver of the car, an 18-year-old man, has been arrested by police.

What happened?

The Newcastle Knights team bus was due to pass through the area as streets were lined with Knights fans farewelling their team to Sydney for Sunday's NRL grand final.

A short time later, NSW Police said emergency services had responded to reports multiple people had been struck by a vehicle at the Transfield Drive roundabout at Wallsend about 9:30am.

"The driver of the vehicle was arrested at the scene," police said in a statement.

Shortly after the incident, the Knights bus diverted to a different route away from the procession of fans.

Several videos seen by the ABC show emergency service helicopters landing on a nearby oval.

Another shows the moment a man from the crashed car was arrested, as an angry crowd shouted in his direction.

Who was injured?

Police said 10 people were taken to hospital, two of whom — a five-year-old girl and a 67-year-old man — were in a critical condition.

The other eight were treated for injuries and include another five-year-old girl, a two-year-old girl and a 63-year-old woman.

They remain in a stable condition.

"So many people have been affected by one person's split-second decision," Police Minister Yasmin Catley said at the scene of the crash.

"What happened is an absolute tragedy, a tragedy that needn't have happened."

What we know about the driver

Police have said the driver was an 18-year-old P-plater.

Assistant Commissioner David Waddell said the man would likely be charged this afternoon, after undergoing drug and alcohol testing.

"Unfortunately a young 18-year-old P-plater driving erratically has lost control of the vehicle and gone into the crowd," he said.

Police said the incident was not targeted and that thousands of people were lining the streets when the car struck members of the crowd.

Assistant Commissioner Waddell said the crowd sought to stop the driver, as well as two passengers who were also in the vehicle, in the ensuing fracas at the scene.

Loading...He praised the efforts of those in the crowd who helped to provide first aid to those injured.

How have people responded?

Knights director of football Chris James made a brief statement when the team arrived in Sydney.

"The thoughts of everyone at our club are with those impacted by this event [including] their families and … those on scene," he said.

The club said it would not make further comment as it was a police matter.

Newcastle Lord Mayor Gavin Morris said the city would "come together for those injured and the families".

"But we will also come together for the Knights," he said.

"It's obviously shifted the entire mood but we will get through this."

Loading...NSW Premier Chris Minns described the incident as a "tragedy" for the Newcastle community.

"It's heartbreaking to see fans who were sending off their grand final team involved in such a terrible incident," he said.

"My thoughts are with the families and friends of loved ones who have been involved or injured in the crash.

"I also want to thank emergency services including police and ambulance who are responding to this tragedy."