Weapon not found from Vic knife attack

A teenager and a knife are being sought in relation to a attempted sexual assault in Melbourne.

A 31-year-old woman was walking her dog at a reserve in Altona when she was grabbed from behind by a male carrying a knife and wearing a bandanna on Wednesday morning.

The male tried to drag her into nearby bushes, but escaped when a passing cyclist disturbed him, police said.

Detective Acting Senior Sergeant Michael Phyland says the knife used in the attack has not yet been recovered and they are concerned the situation could get worse.

Sen Sgt Phyland say they want to speak to teenager Jake Taylor-Cain, who turned 17 on Thursday.

"Our investigation has established Jake as a person of interest," Sen Sgt Phyland said.

"I won't go into the details of how we established that at this stage, other than we would like to speak to him as a person of interest."

The teenager has been urged to hand himself in or make contact with police.