No terrorism link has been identified after a man drove into crowds in Melbourne, the Australian Prime Minister has said, but he added that nothing should be ruled out.

The man who rammed the crowd is a 32-year-old Australian citizen of Afghan descent with a history of drug abuse and mental health issues, police said.

Nine foreign nationals are among the 19 people who were injured after the white Suzuki SUV was deliberately driven into people.

They include people from South Korea, China, Italy, India, Venezuela, Ireland and New Zealand..

A young child is among the injured.

Three people remain in a critical condition in hospital, including an 83-year-old man, local media said.

Prime Minister Malcolm Turnbull told a press conference on Friday: "Our consular officials are working hard to get in touch with their families and make sure they're aware of what's happened to their loved ones."

He added that "no terrorism link has been identified" but that "nothing should be ruled out."

"This was a despicable and cowardly act," he said. "But I want to reassure Australians that this is an isolated incident.

"We should continue to go about our daily lives the way we always do."

The area was put on lock-down and officers warned people to stay away.

Police say they are still investigating whether there was any terrorism-related motive behind the attack, but that early indications suggest there wasn't one.

Premiere of Victoria, Daniel Andrews, described it as "an act of evil and an act of cowardice, perpetrated against innocent bystanders".

Pictures from the scene show the vehicle with a crumpled bonnet crashed into a bollard at a cable car stop.

Witnesses said there were "people flying everywhere", with the crowd rushing to help the injured lying on the road.

A second man, a 24-year-old who was filming the attack on his phone, was also arrested.

He was carrying a bag containing three knives, but is not believed to be connected to the attack and police say they have not established any relationship between the two men.

source: SkyNews