The so-called "dark web" fosters marketplaces where people can deal in drugs, weapons and stolen credit card anonymously.

Police are investigating a "dark web" site trading in illegal and prescription drugs, supposedly being run by three Wellington computer science students.

Party drugs, painkillers, and fake doctors' scripts are for sale on NZ Underworld, claimed to have been started by Victoria University students who have challenged police to catch them if they can.

The anonymous marketplace currently has about 150 members, who join by invitation only. About three new users joined each day, and were vetted online to keep out undercover police, the founders claimed.

Victoria University said it did not know who ran the site, but had expressed concerns to police.

A police spokeswoman said the National Cyber Crime Centre could be called in to help the investigation.

"We cannot go into further detail, due to the nature of the investigation. However, suffice to say that anyone who uses the internet to sell or distribute controlled drugs is committing an offence and should be aware that police will continue to investigate illegal activity online."

The founders of the site claim to be part of a counter-culture movement bridging a gap in supply and demand.

"Drug raids are at an all-time high, and prescriptions are harder than ever to get – and we and our users can't help but feel that this does nothing to help communities."

One seller posting on the site claimed to have a "huge stash" of anti-psychotic drug Seroquel, meant for schizophrenia patients, and advertised the pills as a study aid. A buyer gave them positive review, telling fellow users they bought 30 pills and received them by post.

Another seller was offering counterfeited prescriptions for sedatives and hypnotics at $30 apiece, explaining they would forge the signature of an out-of-town doctor.

The founders said they made money by taking a 1.5 per cent cut of every bitcoin transaction. One bitcoin is currently worth about $450.

They would not reveal how much money they had made so far, saying only: "It's enough to keep three students happy."

Victoria University is unhappy about the site, which was originally launched as "Vic Underworld" using Tor (The Onion Router) software this June.

Tor is a gateway to the "dark web" – home to global drugs supermarkets such as the Silk Road, which was shut down by the FBI in 2013.

This month a 20-year old student was jailed for seven years for importing a "supermarket of drugs" worth $167,000 from the Silk Road via post office boxes around Dunedin.

In June, a 31-year-old Horowhenua man was jailed eight years for importing packages of methamphetamine, ecstasy and LSD ordered online from Las Vegas to his mother's house.

The NZ Underworld founders said they did not envisage their site being used only to sell illegal goods.

"We don't compare ourselves to the Silk Road, mainly because their purpose was explicitly to buy and sell drugs. Our platform has the ability to adapt to current demands and is therefore more reflective of contemporary society."

They said they expected criticism. "We would strongly encourage [people] to be more open-minded, and actually examine the moral and ethical implications for substances that are classified as 'illegal'.

"Alcohol and smoking, for example, is significantly more life-threatening than taking weed ... yet the first two are legal and the third is not."