Police are following up leads into the sex attack on a teenage girl in central Wellington early on Sunday morning.

The 17-year-old was not hurt, but left shaken and traumatised after being indecently assaulted on Courtenay Place about 3.20am.

She was standing near the bus terminus on Courtenay Place waiting for a lift from her boyfriend when a white van pulled up beside her, Detective Constable Trevor Collett said.

"The white van was full of young males and people may remember seeing it because they were shouting out and being unruly," he said.

One man got out of the van and approached the young woman.

"The male grabbed the victim and indecently assaulted her before she managed to break free," Mr Collett said.

"The victim locked herself in a public toilet cubicle...and waited until the offender left."

Mr Collett said police had received several calls from the public regarding the incident.

They were being followed up today and that he hoped to know more about the attack by this afternoon.

The offender was described as 18 to 25 years old, Caucasian, with blonde hair of medium length, and about 1.75m tall, or slightly taller. He had quite big dark eyebrows, was clean shaven, and of muscular build, although not big.

He spoke with a New Zealand accent and was wearing a striped or chequered shirt with the sleeves rolled up and dark coloured trousers, possibly jeans. He smelled of alcohol and was unstable on his feet.

The offender's vehicle was described as a white van, full of boys. It was quite old and not in good condition. It had a black line down the whole length of the side.