A 29-year-old Frenchman shouted "Allahu Akbar" (God is Greatest) as he stabbed a British woman to death and wounded two people at a backpackers' hotel in northern Queensland, police said today.
The man was in Australia on a valid tourist visa and had no known links to radical groups such as Islamic State, which has urged its followers to attack civilians with knives or other readily available weapons, police said.
A 30-year-old British man was in critical condition in hospital after the attack south of the city of Townsville late yesterday night.
Police said they were not ruling out any motive.
"Initial inquiries indicate that comments which may be construed of being of an extremist nature were made by the alleged offender," Queensland Police Service Deputy Commissioner Steve Gollschewski told reporters.
"This person appears to have acted alone," he said. "He is a visitor to Australia and has no known local connections, however investigations are ongoing."
About 100 people have left Australia for Syria to fight alongside organisations such as Islamic State, Australia's Immigration Minister said earlier this year.
Australia, a staunch US ally, has been on heightened alert for attacks by home-grown radicals since 2014 and authorities say they have thwarted a number of plots.
The FBI said that it was investigating a similar attack in Virginia, in which the suspect shouted the same words while attacking a man and woman with a knife. Similar attacks have recently occurred in France, Bangladesh and Germany.
There have been several "lone wolf" assaults, including a 2014 cafe siege in Sydney that left two hostages and the gunman dead. Also in 2014, police shot dead a Melbourne teenager after he stabbed two counter-terrorism officers.
In 2015, a 15-year-old boy fired on an accountant at a police headquarters in a Sydney suburb and was killed in a gunfight with police.
Police did not give details of the third person wounded in the attack, which was captured on video and witnessed by more than a dozen people. There was no ongoing threat to the community, Gollschewski said.
A dog was also killed in the attack, he added.