The San Francisco man, Ross Ulbricht, was sentenced by US District Judge Katherine Forrest in a New York court after his conviction in February on seven charges including narcotics distribution and conspiring to commit computer hacking and money laundering.

The judge said the Silk Road enterprise, which enabled more than $200 million (183.34 million euros) in online drug sales using the bitcoin digital currency, had resulted in at least six drug-related deaths. She also cited five people Ulbricht tried to have killed at a cost of $650,000.

Forrest also demanded the forfeiture of $183.9 million in profits made from the Silk Road site, which Ulbricht, 31, operated from 2011 until his arrest in October 2013, using the alias "Dread Pirate Roberts," taken from the film "The Princess Bride."

Ulbricht's lawyer, Joshua Dratel, said an appeal against the life sentence would be made, calling the verdict "unreasonable, unjust and unfair."

Prosecutors had called for more than the 20-year mandatory minimum for such offenses, but had not demanded the life sentence.

Dark market

Ulbricht told the judge before sentencing that he had not built the website out of greed, and denied all wrongdoing.

He said he had wanted "to empower people to make choices in their lives and have privacy and anonymity."

This account was rejected by Forrest, who said Ulbricht was "no better a person than any other drug dealer," citing written evidence in which he admitted to running a "goddamn multi-million-dollar criminal enterprise."

The Silk Road website used the Tor network - a system allowing users to communicate anonymously on the internet - and the bitcoin currency to allow drugs and other illicit goods to be traded easily by dealers in more than 10 countries in North America and Europe.

Prosecutors said the website generated more than $214 million in sales, and created a blueprint for other so-called "dark market" websites trading in a range of illegal products.

Such sites pose a massive challenge to law enforcement agencies, as they are almost impossible to monitor, and enable the operators and users to keep their identities and locations a secret.

tj/jil (Reuters, AFP, AP)