Lower Hutt police say a brazen attack on a woman in broad daylight came out of the blue.
They say the woman in her 30s was walking along the Hutt Riverbank in Melling during her lunch break on Thursday when she was assaulted by a man at knifepoint.
Police said the woman was kicked in the head and stomped on in the attack just before 1pm.
Detective Sergeant Nick Pritchard said the attacker dragged her into the bushes where he sexually assaulted her.
He said the attack was isolated.
"There's been no reports of similar incidents in recent times, in the middle of the day there are a lot of people around."
The attacker was described as being in his 20s, with a slim to average build and light brown skin.
A large team of officers was hunting for the offender.