A man on a motorbike has sexually assaulted several women while they walked or jog along bike paths in Melbourne's northern suburbs, police believe.
Between December 30 and last Friday, the man has attacked five women, aged between 20 and 35, in twilight hours, a police spokeswoman said.
The man was riding his bike along the paths when he approached the women.
Two women told police they were assaulted on December 30 on the Darebin Creek bicycle path - one near Tooth Court, Mill Park about 7pm and the other near Gaze Court, Mill Park, about 7.30pm.
The following day, a third woman said she was attacked on the path, about 8.10pm near Plenty Road, Reservoir.
The other two incidents occurred last Friday - one on the Merri Walk bicycle path near De Chene Parade in Coburg about 8.45pm, and the second about half an hour later on the Western Ring bike path near Alvarado Avenue, Thomastown.
The attacker has been described as wearing a motorbike helmet with a clear visor and riding a small motorbike, possibly with some green colouring, the spokeswoman said.
He is said to be aged between 20 and 30, about 170 centimetres tall with a thin build and olive skin.
Detectives from Epping Sexual Offences and Child Abuse Investigation Unit want anyone with information to come forward and phone Crime Stoppers on 1800 333 000.