Three baboons that escaped a Sydney hospital and “had a bit of a look around the grounds” were being transported from a baboon colony and had been purpose-bred for medical research.

Police were called to a car park near Royal Prince Alfred Hospital in Camperdown about 5.30pm on Tuesday after the baboons made their bid for freedom, a NSW Police spokeswoman said.

They broke out when the lock on the truck they were in failed — bemused onlookers filming the primates as they roamed the hospital grounds and car park on Missenden Road and Lucas Street as police and staff from Taronga Zoo tried to catch them.

The baboons were contained by police and medical experts before zoo handlers tranquillised them.

THEY'RE TAKING OVER!!! #BaboonWatch #baboons2020 (vid Michael Tran) pic.twitter.com/aVbmJhQjV3

— Dougal Wallace (@DougalWallace) February 25, 2020

NSW Health Minister Brad Hazzard said the 15-year-old male baboon had been taken to the hospital for a vasectomy. Two female baboons were there to “keep him calm”.

“The three baboons decided to take a bit of a look around RPA grounds,” he said on Tuesday.

“They didn’t know what to do, nor did the people around them.”

A witness has captured the moment three baboons escaped from a facility near a Sydney hospital as shocked onlookers watched on. #baboonwatch pic.twitter.com/3INAIKKRc2

— Sandra Sully AM 📺🎧📲🏑🌺 (@Sandra_Sully) February 25, 2020

Mr Hazzard insisted the baboons were not being transported for research purposes.

“It had been decided the male needed to have a vasectomy to continue to move with his female troop and not keep producing babies,” he said.

“If he had been kept fertile, he would have had to be removed from the family he knows.”

Tweet from @BradHazzard

The Health Minister said the baboons should be awake and well within a few hours.

It was later revealed they were from the National Health and Medical Research Council facility in Wallacia, about 50 kilometres away in Western Sydney.

According to Humane Research Australia, there were 272 primates used in medical research in the country in 2017. Of those, 165 were in NSW.

Research at the lab has been used to tackle priority medical issues identified by the federal government, including diabetes, kidney disease and complications arising from pregnancy.

Professor Annemarie Hennessy, a senior adviser at the facility, said the animals lived in an environment that resembled their natural habitat.

“They would have been completely terrified outside their comfort zone in a world they don’t understand,” she said of their escape on Tuesday.

She said the facility had used baboons in “important biomedical research” in Australia for at least 30 years – justified only when there was “no alternative”.

Mr Hazzard said the baboons were part of research programs that covered a whole range of health issues. When the program has finished with them, they are returned to their colony.

NSW Police had earlier said there was no immediate danger to the public but people were advised to avoid the area.

Footage shared on social media showed three baboons running in the car park as people took surprised double-takes.

Police hunt for baboons near Sydney’s Royal Prince Alfred Hospital on Tuesday. Photo: AAP

Animal activist and former GP Kevin Coleman said the primates’ escape was a “major concern” that could raise biosecurity issues.

“If an animal the size of a baboon can escape, how many mice have escaped? How many other animals have escaped,” he asked.

“We just don’t know and this is the problem. We have to have transparency on these issues.”

NSW Animal Justice Party MP Emma Hurst said the baboons were “medical experimentation survivors” who were trying to flee “further painful procedures forced upon their bodies”.

“These are the hidden faces behind animal experimentation in this country,” she said.

The three primates were returned to the Wallacia facility late on Tuesday, and the male has had his vasectomy postponed.

Baboons are known to be violent if threatened, but Mr Hazzard said the animals had “behaved impeccably”.

An investigation has been launched into why the truck’s lock broke.

The Sydney Save Animals in Laboratories spokesman said he thought experts were doing research into human-baboon hybrid organs to address the transplant crisis.

Mr Hazzard dismissed these claims.

“It’s rubbish … These baboons were simply there for the old vasectomy,” he said.

-with AAP