A man who dragged an Auckland jogger into bushes before strangling his victim and sexually assaulting her has admitted the random and "repugnant attack".

Avin Ivory Lock appeared in the Auckland District Court last week and pleaded guilty after being charged with assault with intent to commit sexual violation.

Police had arrested the 33-year-old in May after a female jogger was attacked in the early hours of May 11.

The woman was running about 5am on a track alongside Auckland's Northern Motorway.

As she ran towards the city, Lock reached out and grabbed her, dragging her into some bushes near St Mary's Rd.

Police released CCTV footage taken on the morning of the attack.

He then strangled her and began sexually assaulting her.

Fortunately, a passing cyclist heard the woman's screams and came to her aid - courageously chasing away her attacker.

Lock fled and was last seen jumping over a fence and running in the direction of Swift Ave and Hackett St, through the rear of several properties.

Detective Inspector Scott Beard earlier said the victim and cyclist immediately went to the Auckland Central Police Station to report the attack.

The woman suffered minor injuries and was shaken by the incident.

Police later released CCTV footage of the offender in the area shortly before the incident.

It shows him wearing a dark hoody and a cap.

Detective Senior Sergeant Glenn Baldwin said at the time the offender was in Beaumont St, opposite Victoria Park, prior to the incident.

"This was a random attack by a stranger," he said.

Lock faces other charges for offensive behaviour and being unlawfully on property, which he has pleaded not guilty to.

Detective Senior Sergeant Glenn Baldwin said after Lock's arrest a significant amount of resources went into the investigation to solve the "repugnant attack".

"It's a great result to have the alleged offender off our streets," he said.

"We want to assure the community that we will do everything we can to find those responsible for crimes such as this and hold them to account."

Police would not comment further on the case before Lock's sentencing later this year.