A 21-year-old Christchurch woman who was attacked near the city centre last night bit the man's hand hard enough to leave a visible mark.
The woman was attacked from behind by a man as she walked along a street in Waltham, just south of the CBD, last night.
She bit the man's hand during the assault, which the police believe was sexually motivated.
Police said the bite was strong enough to leave a visible mark.
They wanted to hear from anyone who might have seen the man, or witnessed the attack.
He has been described as tall and slim with shaggy hair, and was wearing dark clothing.