Sexual violence agencies say the public have been "left in the dark" following revelations about a possible serial predator, and want an explanation from police.

The groups said women had a right to information about their safety so they could make choices. Equally, if there was no danger, police should publicise that, they said.

"At the moment we're in the dark. And that's how sexual violence exists, in the dark, and public awareness helps prevent it," said national Rape Crisis spokeswoman Andrea Black.

"I think they could at least give the community a clue about what's going on."

The Herald revealed last week that Wellington police were investigating potential links between 12 sexual assault cases in the central city, stretching as far back as seven years.

Detectives were working to establish if a single predator was responsible for the crimes, focusing on similarities in criminal behaviour from each incident.

They include attacks where women were grabbed from behind and dragged into secluded areas.

Two victims spoken to by the Herald were able to fight their attacker off, but it was understood the cases include at least one rape.

Police have so far refused to release almost any information about the case, citing "investigative and operational" reasons.

It was unknown if the offender - it it was a single person - was still active. In a statement issued this week, police referred to the crimes as "historic".

However, the Herald understands one of the incidents was as recent as January 2017.

Sexual violence support agencies said they were disappointed at the lack of transparency and communication following the story.

Conor Twyford, head of the Wellington Sexual Abuse Help Foundation, said ideally, police would be front-footing the situation.

"We know they're doing their best, but it is unsettling for people when these stories come out and police do have a responsibility to communicate."

General manager for Sexual Abuse Prevention Network, Fiona Macnamara, said she didn't expect details of the investigation, but if there were risky areas - such as a path at the Boyd Wilson field linked to a number of attacks - there should be a warning.

"While the conversation should focus on changing bad behaviour - and not on people keeping safe - we're not there yet, so we do need to keep safe," she said.

"For example, I'm not going to be walking near Boyd Wilson late at night now that I know this information."

Police said each of the historic assaults were thoroughly investigated at the time. Some had featured on Police 10-7, and an identikit was released in 2014, they said.

Detective Senior Sergeant Warwick McKee said while he understood the public might want to know more details, at times it was imperative that police maintained confidence around the integrity of its inquiries.

He said victims had been informed of developments and police were continuing to support them.

McKee said if anyone had been the victim of an assault and had not yet reported it, they were urged to do so.