SYDNEY — A sport-utility vehicle driven by an Australian man of Afghan descent with a history of mental illness plowed into pedestrians in Melbourne on Thursday, injuring at least 19 people, four of them critically, officials said.
While the incident bore similarities to recent terrorist attacks in Europe and the United States, and police described the ramming as a "deliberate act," authorities said there was no evidence of terrorist links.
"We don't have any intelligence or evidence to indicate there is a connection to terrorism," said Shane Patton, the acting police commissioner of Victoria state, of which Melbourne is the capital. "Having said that, we continue to support this investigation with the Counter-Terrorism Command to ensure there isn't that connection and there is no ongoing threat."
A second man seen recording the incident on a cellphone was arrested after three knives were found in a bag he was carrying. But Patton said there was no sign the man was involved.
Witnesses said the white Suzuki SUV did not appear to brake as it plowed through one of the main intersections in Australia's second-largest city, full of Christmas shoppers and commuters. It finally crashed into a streetcar stop and came to a halt.
"All you could hear was bang, bang, bang, bang," Jim Stoupas, the owner of a nearby doughnut shop, told the Australian Broadcasting Corp. "The only thing that slowed him down was hitting pedestrians. All you could hear were the sounds of the car hitting people and the screams."
The driver was apprehended by an off-duty police sergeant who held him until police arrived, with both sustaining injuries in the struggle.
Police said the man, whose name was not immediately released, had a history of drug use and mental health issues, and was known to them for traffic offenses and a minor assault in 2010. He was taken to a hospital, where doctors are to determine when he will be fit to be questioned by police.
"What has occurred on Flinders Street was an act of evil and act of cowardice at a time of year when people should be out celebrating and doing their Christmas shopping," Daniel Andrews, the premier of Victoria state, told a news conference. He said 19 people were hospitalized, four of them in critical condition. Australian media outlets reported that one of those critically injured was a child of preschool age.
Patton said the Australian intelligence agency and federal police had no information indicating that the driver of the SUV was someone to be watched.
"We understand he's on a mental health plan and receiving treatment for a mental illness," the acting police commissioner said without elaborating.
The incident took place in downtown Melbourne during one of the busiest times of the day in front of a train station that is the city's equivalent of New York's Grand Central Terminal.
The mayhem unleashed on a downtown street filled with Christmas shoppers and late-afternoon revelers was reminiscent of a string of lone-wolf terrorist attacks in Europe — including Spain, France and Germany — in which attackers used vehicles as deadly weapons.
A long-standing military ally of the United States, Australia has deployed forces to Iraq and Syria to assist with the fight against the Islamic State.
It was the second time this year that Melbourne has been struck by a vehicle attack. In January, a driver killed six people and injured more than 30 when he ran over pedestrians not far from the scene of Thursday's incident. In that case, the perpetrator also had drug and mental health problems, and police found no link to terrorism.
Nevertheless, government officials have warned the public of the likelihood of terrorist violence in Australia, and Melbourne recently decided to install a public address system in the downtown area to warn of an attack, according to media reports.
Melbourne Mayor Robert Doyle said two weeks ago that the city faced the threat of an individual inspired by a foreign terrorist organization.
"That's always going to be hard to stop, but so far our intelligence services and our police have done a magnificent job in keeping us safe," he said in an interview published Dec. 7.
Vehicle attacks have become a common choice of Islamic State-inspired terrorists, and they are among the hardest to stop, given the easy accessibility of cars and small vans compared with explosives or firearms.
In the most devastating vehicle attack so far, more than 80 people were killed by a truck in the southern French city of Nice last year.
In London, the driver of a van plowed into a group of people on Westminster Bridge in March. Investigators later found indications that the incident constituted "Islamist-related terrorism."
In October, a pickup truck sped down a bike path in New York City, killing eight people before colliding with a bus. In a handwritten note, the driver had pledged allegiance to the Islamic State.
On Tuesday, Germans commemorated the anniversary of a vehicle attack on a Berlin Christmas market last year in which 12 were killed and more than 50 injured.
Schemm reported from Addis Ababa, Ethiopia. William Branigin in Washington and Rick Noack in Berlin contributed to this report.