Police have shot and killed a man in central Brisbane, after he broke the nose of a male tourist and stabbed him in the back.

Key points: Witnesses say police fired up to 10 rounds at the knife-wielding man

Witnesses say police fired up to 10 rounds at the knife-wielding man Police say he confronted officers shortly after attacking two overseas tourists

Police say he confronted officers shortly after attacking two overseas tourists A 26-year-old tourist suffered a broken nose and a stab wound to his back

It is understood the attacker was still wielding a knife when officers shot him outside the Westin Hotel on Mary Street about 10:00am on Sunday.

Detective Superintendent Tony Fleming said police believed the offender, aged in his mid-20s, acted alone.

He said the man confronted two overseas tourists, a man and a woman, with a knife.

The male tourist was struck in the face and suffered a broken nose and cut lip.

Taxi driver Rubal Singh captured the moment two police officers confronted a man with a knife, moments before they shot him. ( Supplied )

Superintendent Fleming said police did not believe the attack was racially motivated.

He said officers in the area were made aware of the incident.

"A police crew coming down Mary Street saw the person who fit the description [of the attacker]," he said.

Forensic police examine the scene. ( AAP: Glenn Hunt )

A police statement said it would be alleged the man "charged at officers and was critically injured when police returned fire".

Superintendent Fleming said the tourists described the man's behaviour as strange.

"It's my understanding that what the police were confronted with today was a life-endangering situation to them and I'm very pleased that they are alive, but it is tragic that a young man has died," he said.

Superintendent Tony Fleming said the situation escalated rapidly. ( ABC News )

Superintendent Fleming said the male tourist, 26, was taken to hospital where he received a single stitch and he had since been released.

He said the shooting would be reviewed by police ethical standards investigators, the Crime and Corruption Commission and the Queensland coroner.

'At least 10 rounds fired'

One witness said police asked the man several times to put down the knife and when he failed to comply, they shot him.

Nearby residents said they ran for their lives as the shots were fired.

Taxi driver Rubal Singh was metres away when the shooting unfolded and captured video on his mobile phone of police confronting the man.

Brisbane taxi driver Rubal Singh witnessed the shooting. ( ABC News: Lexy Hamilton-Smith )

"I couldn't see anyone threatening but all I could see was the cops jump out of the car and start shooting," he said.

"At least 10 rounds [were] fired and I witnessed it with my own eyes, like 10 feet away from the car.

"Cops started shooting the guy and I then saw one of the cops kicked away the knife on the ground.

"It was horrendous. I was about to finish my shift and it was shocking to see such an incident happen in front of you.

"The man was out of the car — he got shot at least 10 times. I think he was alone."

'It was a lot of shots'

Adam Leishman, who lives in an apartment above the Westin Hotel, said he was nearby and heard the shots fired.

"All of us in there just heard the shots and started running really quick … it was a lot of shots," he said.

"Me and about 20 others were in the alleyway and we had no idea who was behind the gun.

Police outside the Westin Hotel in the Brisbane CBD, after the shooting. ( ABC News: Lexy Hamilton-Smith )

"We moved pretty quickly when we heard the shots.

"It is comforting to know if there are going to be shots fired in Brisbane it is in the hands of a policeman and not someone who shouldn't have a gun."

'Happened very quickly'

Superintendent Fleming said the man who died was known to police.

"But the specifics of that I'm not going to go into at the moment," he said.

"I don't have any information that confirms or makes this an active CT [counter-terrorism] investigation."

"But I want to stress the fact … all the information to us at the moment is that this person was acting alone, came into the city alone, did those actions alone, but we just don't take anything for granted.

"The advice we have is he confronted these people on the street and things escalated.

"This is just two people — visitors to our city — who've been confronted by a man in a terrifying incident for them and the police officers involved.

"They are shaken, this was a very rapid series of events, this was a very confronting situation for them and this has all happened very quickly."

He said an autopsy would be conducted to examine whether drugs or alcohol were a factor.