Car mows down pedestrians outside Melbourne's Flinders Street station

Key Points:

• A vehicle has struck pedestrians on Flinders Street in Melbourne
• The incident happened during rush hour, at approximately 4:45pm
• The driver of the vehicle and a second man have been arrested and are in police custody
• Police say 14 people are injured, several critical

Police say 14 people are injured, several in a critical condition, after a car ploughed into pedestrians in central Melbourne.

The car hit and injured a number of pedestrians outside Melbourne's Finders Street station, then crashed into a bollard.

Ambulance Victoria said paramedics were assessing people at the scene of the incident and police have held a media briefing.

Commander Russell Barrett of Victoria Police said they believe the crash was deliberate but said it's too early to speculate on the motivations of the driver.

"At this stage we believe it is a deliberate act however we do not know the motivation and it is still early stages of the investigation."

The driver of the vehicle and a second man have been arrested.

The two men have not yet been charged, police said at the press conference.

Police and emergency services will stay at the scene for "a considerable period of time" and are urging people to avoid the area.

Footage taken by a witness shows a man in a white shirt and blue jeans being dragged from the passenger side of the vehicle.

Another witness photo shows a bearded man in a red and black chequered shirt sitting on the ground with his arms cuffed behind his back.

A preschool-aged child with serious head injuries is among the injured and has been transported to Royal Children's Hospital in a serious condition.

There are reports that 13 people have been taken to The Royal Melbounre and Alfred Hospital for treatment.

Witnesses described horrific scenes of "people are flying everywhere" as the carnage unfolded at the corner of Elizabeth Street and Flinders Street at 4.41pm this afternoon during peak hour.

A spokesperson for Victoria Police said in a statement: "Police are currently attending an incident on Flinders Street between Elizabeth and Swanston streets where a vehicle has collided with a number of pedestrians.

"Police have arrested the driver of the car. Extent of injuries are not known at this stage.

Ambulance Victoria said in a statement: "Paramedics were called to a report of pedestrians hit by a car at the corner of Elizabeth Street and Flinders Street at 4.41pm this afternoon. Paramedics are on scene."

The vehicle ran a red light just after 4.30pm, witnesses have told 3AW, before mowing into pedestrians.

Other bystanders said the vehicle made "no effort to slow down".

A witness, Sue, from Walker's Doughnuts, told 3AW's Brianna Travers: "We could hear this noise, as we looked left, we saw this white car, it just mauled everybody down. People are flying everywhere. We heard thump, thump. People are running everywhere."

Witness Lauren Lopatko tweeted: "Something just happened outside Elizabeth st tram stop outside Flinders St station. Avoid area if you can. I saw ppl screaming & smoke.

Another witness, Frank, posted "I've counted 5 cop cars and an ambo coming up the tram tracks towards Flinders along Elizabeth Street ... Make that two ambos. Beat coppers were running down on foot too. Something big defs going on but not sure what."

He then updated, saying: "I've lost count how many coppers and ambos have come past now. Standing the tram stop out front of GPO."

A crime scene has been established and all vehicular and pedestrian traffic are advised to avoid the area. Members of the public with video footage or images have been encouraged to upload them here.

Australian Prime Minister has tweeted his condolences to those affected, as has New Zealand Prime Minister Jacinda Ardern.

Today's incident has brought parts of the city to a standstill four days out from Christmas.

In January this year four people were killed and 29 injured when a man drove a car through Melbourne's Bourke St mall.

Heavy concrete bollards have since been placed at key spots around the city, including at Flinders St Station, to prevent vehicles ploughing into pedestrians on footpaths.

Witnesses have praised the response from police, who were at the scene on Flinders St within minutes.

Melbourne's police force had just days ago introduced new Critical Incident Response teams, with teams of armed undercover police officers, some in unmarked vehicles, patrolling the CBD ready to respond to major incidents such as terror attacks.