Police are calling for help to identify a man after a woman was indecently assaulted in Greenlane last Friday.

At about 4pm the woman was walking home on Great South Rd when she was approached by a man who started walking with her. She was heading along Rockfield Rd, turned into Oranga Ave and finally went into Oranga School.

When the woman entered the school the man grabbed and indecently assaulted her, police say.

She managed to stop the assault which was witnessed by another person who intervened and called police.

The offender fled.

Police say the victim's quick thinking and the intervention by another person prevented a more serious offence from occurring.

The man is described as a Polynesian in his early 20s. His face is marked with acne and he has the word "TOA" tattooed on one of his hands.

He was wearing a black hooded sweatshirt with a logo on the front, dark jeans and white shoes. Police believe he may live in the Oranga area.

If you have any information, call Detective Sergeant Kath Bostock on 5241920 or Crimestoppers anonymously on 0800555111.

- © Fairfax NZ News