UPDATED AT 20:35:

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

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.

Sky News is reporting that the driver of the vehicle and a second man have been arrested.

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

There are reports that 14 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."

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. (1/2)

— Victoria Police (@VictoriaPolice) December 21, 2017

Police are asking any witnesses to go to the Melbourne West Police Station at 313 Spencer Street, Melbourne and all vehicular and pedestrian traffic to avoid the area. (2/2)

— Victoria Police (@VictoriaPolice) December 21, 2017

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."

Absolute chaos in Melbourne's CBD. Several people run down by a driver on corner of Elizabeth and flinders St @theheraldsun pic.twitter.com/2uBHvEIggX

— Cassie Zervos (@cassiezervos) December 21, 2017

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."

MAJOR unfolding incident in Melbourne's CBD.

Sue from Walker's Doughnuts: "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." @3AW693

— Brianna Travers (@briannatravers) December 21, 2017

A crime scene has been established and all vehicular and pedestrian traffic are advised to avoid the area.

If members of the public have video footage or images, which may assist police with their investigation, they are encouraged to upload them to here.

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 were placed at key spots around the city, including at Flinders St Station, to prevent vehicles ploughing into pedestrians.