BONDI — Eyewitnesses have described scenes of chaos as they fled a busy Sydney shopping mall where a knifeman killed six people and wounded several others.

"It was carnage," said a witness, who was in a cafe nearby with his two young children as the attack began.

The man, who did not want to be named, told ABC News he saw a man suddenly "stabbing people indiscriminately".

Crowds poured from Westfield shopping center in Bondi when the terrifying incident began just after 3pm.

"It was insanity," a visibly upset woman said, as she described seeing a wounded woman lying on the floor.

Police say the knifeman had visited the mall at 15:10 local time before returning minutes later to begin his rampage.

The attack was only ended when a female police officer - who had been on duty nearby - confronted the man. He raised his knife towards her and she shot him, police said.

Jason Dockson said he heard "people yelling and screaming, running" and began following behind the officer.

He said the man, armed with a "big blade" started "floating towards us and all I heard was 'put it down' and then she shot him".

"If she didn't shoot him, well, he would have kept going, he was on the rampage."

Prime Minister Anthony Albanese described the officer as a "hero", saying: "There is no doubt that she saved lives through her action."

"For all of us tonight, the devastating scenes of Bondi Junction are beyond words or understanding," he said.

The Westfield mall where the attack took place is a major shopping centre in the east of Sydney's central business district and close to the famous Bondi Beach.

It is one of the biggest and most popular shopping centres in the country and like any other Saturday was packed with hundreds of people, including many families and young children.

Horrified shoppers have described their shock as the attacks unfolded.

Johnny, 33, who was visiting from the New South Wales Central Coast, said he heard a commotion while shopping and turned to see a woman and her baby being attacked.

"She was getting stabbed. Everyone was in shock [and] didn't know what to do," he said.

Nearby he thought he could make out another body on the ground, he said.

The injured woman managed to make a run for the Tommy Hilfiger store and once inside, staff quickly locked the doors, he said.

"Some of the other shoppers were using clothing and things to try and... stop the bleeding," he said.

"The baby only had a minor wound, but the lady was pretty bad... there was a lot of blood and she was panicking," he added.

"Hopefully she pulls through."

Rashdan Aqashah, who was working in clothing store COS, said he saw a man holding a pole confront the attacker on an escalator.

"I saw this one guy fighting with the killer. He was holding the pole, trying to throw a pole at the escalator," the 19-year-old said.

Mr Aqashah said "everyone started running" when the attack began unfolding.

"I grabbed my manager to shut the store door. It was just in front of our store," he said.

Olinder Nemer told the BBC she scene was "so scary".

"I didn't see him stabbing people, but I saw him running with the knife," the 22-year-old said.

"People were just running, screaming. At first we didn't know what was happening, so we were running with everyone."

Vernon Michael told Reuters he was in a store when he heard someone saying "run, run, run, someone's been stabbed".

"We're just grateful cause like literally two minutes before that, we were sitting right where it happened, where the first lady got stabbed," he said.

Another eyewitness told Reuters news agency they saw someone lying down injured and were looking to see what was going on.

"Then we saw all these people running towards us and then we heard a shot and my husband dragged us into the Adairs shop and then we got the lady there trying to lock the doors and then she couldn't lock the front door, so we went in the office which was all locked and then we were in there until the police came to get us."

Police said five women and a man had died as a result of the attack, while a nine-month-old baby required surgery.

About eight people, including the child, are being treated for different injuries as a result of the attack, New South Wales Police Commissioner Karen Webb said.

She added officers believed they had identified the attacker as a 40-year-old man but were waiting to officially confirm his identity.

If the man is who they believe him to be, then police did not consider the motive to be terrorism, she said. — BBC