A man has been arrested after a police officer was allegedly stabbed multiple times in the back of the head in Sydney's CBD on Sunday.
The incident unfolded just after 1pm when a 33-year-old man wielding a knife about 30 centimetres long confronted two police officers on traffic duties on the corner of Castlereagh and Park Streets, near Hyde Park.
He didn't say anything to the officers as he approached them.
"[The man] stabbed the male constable in the back of the head a number of times," Detective Superintendent Martin Fileman said.
"The injured officer and a female officer then gave chase along Park Street off to Hyde Park near Elizabeth Street, where assisted by other police officers, that offender was arrested."
Paramedics treated the officer for non-life threatening injuries at the scene before he was taken to St Vincent's Hospital, where he remains in a stable condition with two skull fractures.
Two crime scenes were established, one at the corner of Castlereagh and Park Streets, and the other near where the man was tasered before being arrested.
Superintendent Fileman said the knife remained in the man's hand until his arrest, where he was "demanding that police shoot him".
He was known to police for minor matters and according to Superintendent Fileman "there is no history of mental illness on our database".
The man was taken to Royal Prince Alfred Hospital for assessment and was under police guard.
He was expected to be released shortly and will be facing "very serious charges".
Superintendent Fileman praised the action of officers, particularly the constable who continued working despite his injuries.
"Just shows you the type of training that we go through," he said.
"We're faced with a situation that you know, if an officer is injured that they keep going, and this officer did, this officer gave chase."
Detectives are investigating the motives behind the man's attack.
'Sorry for people of Sydney'
A witness told the ABC he saw a "lot of cops" rush in and "hold the man down".
"It looked like he was riding a push bike," he said.
"They just came, had him on the ground and held him there."
Shireen Hayes and her family were having lunch at Hyde Park after visiting the museum when they heard the police sirens.
"It was just a bit scary because we could see all the cops were in one area and cordoned it off pretty quickly," Ms Hayes said.
"There seems to be a lot of that happening at the moment [stabbings] so that's really concerning."
North coast resident Maree Ahern had also spent the day at the museum with her family after being reluctant to travel to Sydney due to the recent stabbings.
"We sort of feel that we have to be very aware of our surroundings now more than we ever did before," Ms Ahern said.
"And we watch now as to who is around us because we are a little bit nervous about coming to Sydney."
She said she was shocked by the event.
'We feel very sorry for the people of Sydney who have to live with this every day.
"We just feel now that the city is not quite as safe as it used to be. Yeah, so it's very sad for the policeman that's been stabbed."
The stabbing comes a little more than a month after six people were killed by 40-year-old Joel Cauchi with a knife at Westfield Bondi Junction.
Ashlee Good, Dawn Singleton, Jade Young, Pikria Darchia, Faraz Tahir and a Chinese national whose family has asked she not be named, all died in the attack.
A few days later, a 16-year-old boy was arrested after allegedly stabbing Bishop Mar Mari Emmanuel at a live-streamed church service in the Sydney suburb of Wakeley.