Three Britons have described the "very surreal" moment they apprehended a knife-wielding man in Sydney moments after he allegedly stabbed a woman to death.
Footage posted online appears to show a suspect standing on a vehicle roof, holding a knife aloft and shouting, before being taken down by bystanders, who caged him by trapping him in chairs.
Police and witnesses said the knife-wielding man yelled "Allahu akbar", or "God is great", and attempted to stab several people in the Australian city before being arrested.
READ MORE: Rise in number of armed police patrolling Lancashire's streets
New South Wales Police said in a statement: "Inquiries are under way after the body of a woman was found inside a unit on Clarence Street, Sydney, about 3.15pm (0615 BST) today.
"Officers from Sydney City Police area command are on the scene and will conduct inquiries into whether the incident is linked to an earlier stabbing at a hotel on the corner of Clarence and King streets."
Lee Cuthbert, Paul O'Shaughnessy and Luke O'Shaughnessy, all from Manchester, were working in the area when they heard the man attempting to stab several people outside, according to the Sydney Morning Herald.
Mr Cuthbert told the Australian paper: "We had a window open to get some air in and then we just heard the commotion ... we looked out and saw him on top of a car, wielding a knife, and we all just kind of reacted from there.
"We just tried to get down as quick as we could. You don't think, you just kind of react really, it was surreal, very, very surreal.
"We all kind of chased, worked together, but it was Luke who was the real hero. He pursued him the hardest and managed to get a grip of him."
The three friends, who all work at a recruitment agency in the city, helped tackle the man alongside an Australian colleague.
Australian Prime Minister Scott Morrison praised the "brave" people who tackled the knifeman.
He posted on Twitter: "The violent attack that took place in Sydney this afternoon is deeply concerning.
"The attacker is now in police custody following the brave actions of those who were present at the scene and able to restrain him.
"The motivation for this attack has not yet been determined as police are continuing with their enquiries.
"Our thoughts are with all of those who have been impacted by this violent attack."
NSW Police Superintendent Gavin Wood, speaking to reporters near the scene, said: "A number of members of the public actually physically restrained the offender.
"And I want to acknowledge those people, those members of the public who got involved. They are brave, and I can only use that word seriously.
"They are significantly brave people. They approach the person... with clear evidence of a stabbing previously.
"These people are heroes, and I want to acknowledge that."