A preschool aged child is among the victims after a car ploughed into shoppers in Melbourne's CBD.

A preschool aged child has been rushed to hospital with a head injury after an SUV ploughed into shoppers in Melbourne’s CBD.

Early reports indicate that a number of people are being treated at the scene, with nineteen people, including the child, taken to hospital, some in critical condition.

The car collided with shoppers during the busy Christmas season close to Flinders street station.

Police have described the incident as a “deliberate act”.

A pre-school aged child suffering a head injury is among those hurt, and has been rushed to the Royal Children's Hospital in a serious condition, Ambulance Victoria says.

The child is not in a critical condition.

Aerial footage of the scene shows a white Suzuki SUV crashed into a tram stop.

The vehicle ran a red light just after 4.30pm on Thursday, witnesses have told 3AW.

The driver has been arrested. He is a 32-year-old Australian citizen, and was known to police. He was a history of assault, drug use and mental health issues. He is receiving treatment for a mental illness, Victoria Police said in a statement.

There was only one man present in the car, with a second man, who filmed the incident from the street, found in possession of knives and also taken into custody. It is not clear if the 24-year-old man has any links to the driver.

Police stressed that they have no indication or evidence to support a link to terrorism.

“Police have arrested the driver of the car. Extent of injuries are not known at this stage,” Creina O’Grady, a police spokeswoman told the Sun Herald.

Eyewitness said the car was going at least 100km, and "only stopped because it was ploughing through people".

"Unless he had some kind of medical episode, this has to have been deliberate," the witness is reported to have said.

At least one other person has been taken to The Alfred Hospital in an unknown condition.

"As it (the car) approached this intersection ... it just mowed everybody down, people were flying everywhere," witness Sue told 3AW.

Thursday's incident on Flinders Street between Elizabeth and Swanston streets has brought parts of the city to a standstill four days out from Christmas.