Video has emerged of a man being arrested after a car was driven into pedestrians in Australia's second largest city.

Up to 19 people were injured, four critically, when the white SUV was driven at crowds outside Flinders Street station in Melbourne in what officers called a "deliberate act."

The footage shows police pin the man to the floor as they pull his arms behind his back and put him in handcuffs. He was wearing a white shirt and blue trousers.

Police said the driver was a 32-year-old Australian of Afghan descent, with a history of drug use and mental health problems.

Victoria Police chief Shane Patton said a second man, aged 24, who was arrested after he was seen filming the incident was found to have a bag containing knives.

Investigators have found no evidence to suggest a link with terrorism and Mr Patton said they had not established any relationship between the two men.

Melbourne car crash Show all 12 1 /12 Melbourne car crash Melbourne car crash Police and emergency personnel work at the scene of where a car ran over pedestrians in Flinders Street in Melbourne REUTERS Melbourne car crash The white car surrounded by investigators ABC Melbourne car crash A police officer detains a suspected man Twitter/LACHLANVE via Reuters Melbourne car crash People have been injured, some seriously after the crash PA Melbourne car crash Victoria Police Commander Russell Barrett speaks to the media on Flinders Street AAP/Joe Castro via Reuters Melbourne car crash Police and emergency services attend to the scene Reuters Melbourne car crash The white SUV sits in the middle of the road AFP/Getty Melbourne car crash Members of the public stand behind police tape after the driver of a vehicle that ploughed into pedestrians at a crowded intersection was arrested Reuters Melbourne car crash Police and emergency personnel work at the scene AFP/Getty Images Melbourne car crash Police and emergency services attend the scene of the crash on Flinders Street Reuters Melbourne car crash The scene where a car ran over pedestrians AFP/Getty Melbourne car crash Police and emergency personnel examine the scene of where a car ran over pedestrians AFP/Getty

Earlier, Commander Russell Barrett told media that while the motive of the incident was not immediately clear, "at this stage we believe it was a deliberate act."

He confirmed 14 people had been injured in the attack.