The female constable who died instantly in a horrific police car crash in Sydney’s Redfern on Friday morning had only been on the force for 16 months.

Police Commissioner Mal Lanyon said Mia Lay, 20, showed “exceptional promise” as a young officer and was “well-loved” in the South Sydney Police Area Command.

“She would have been an outstanding police officer and to lose a life both in its prime and just at the infancy of becoming a police officer is a terrible tragedy,” he said on Friday.

The police car Lay was travelling in as a passenger slammed into a tree while the vehicle was under lights and sirens.

The two officers were responding to a stolen vehicle report in Glebe when the accident happened on Gibbons Street, in Redfern, about 1.30 Friday.

Lay died instantly. Paramedics treated the male constable, 24, who was driving before he was taken to hospital in a stable condition.

News.com.au said CCTV showed the dramatic moment of the crash, with the car bursting into flames on impact.

The driver crawls out from the wreckage and checks on his passenger before other officers arrive and usher him away from the devastating scene.

Constable Mia Lay was a young recruit who loved her job. Photo: Supplied

Lanyon said an investigation would look into the cause of the crash.

“It is important to understand the circumstances. When officers are travelling on urgent duty, have lights and sirens on, they are exempt under the Australian road rules, so they can exceed the speed limit.

“As the Commissioner, what I’m keen to do is to make sure our officers are as safe as possible and the best and only way is to examine these scenes thoroughly so we understand what happened.”

Lanyon said it was a “terribly difficult day'” and offered his condolences to Mia’s family, friends and loved ones.

“There is nothing I can say easily that takes the pain away but know that Mia was a loved police officer.

“As police officers, we understand the risk of what we do, we put our lives in the way for the safety of the community to prevent crime and to make sure the community is safe.

“Terribly, on some of those days, some police officers pay the ultimate sacrifice.”

The crash scene on Gibbons Street, Redfern. Photo: AAP

Police Yasmin Catley said Lay was a “beautiful young woman” who “loved what she was doing”.

“But tragically she went to work yesterday and she didn’t go home and that is incredibly sad,” Catley said.

“We ask so much of our police and I often say it’s a job like no other but to not go home, to lose one of our precious colleagues, is a very, very sad and dark day.”

The NSW Police watchdog said it would monitor the force’s investigation into the crash to “ensure public confidence”.

The Law Enforcement Conduct Commission said it could not independently investigate the incident until NSW Police finishes its probe, and any coronial or criminal proceedings are over.

Opposition Leader Kelly Sloane said she was “heartbroken” by the news.

“(The officer) was out working while most of us were asleep, protecting the community,” she said.

Nearby Regent Street remained closed in both directions between Lawson and Cleveland streets.

Motorists were advised to avoid the area, with several bus routes being diverted.

-with AAP