The FBI has shut down an online black market used to buy drugs and hitmen, and arrested its suspected mastermind.

Ross William Ulbricht, 29, is accused of “controlling and overseeing all aspects” of hidden website Silk Road, as well as plotting to kill another person who was trying to extort him.

Ulbricht, known as Dread Pirate Roberts on the site, is also charged with drug trafficking, computer hacking and money laundering.

Silk Road has been dubbed ‘eBay of the drug trade’

The website, dubbed the eBay of the drug trade, used a privacy-protecting Tor network and Bitcoin digital currency to shield the identities of buyers and sellers around the world.

As they busted the site, authorities seized approximately $3.6m (£2.2m) worth of Bitcoins – the largest-ever seizure of the currency.

FBI agent Christopher Tarbell said Silk Road was used by “several thousand drug dealers” to sell “hundreds of kilograms of illegal drugs”.

The website allowed users to anonymously browse through nearly 13,000 listings under categories such as “cannabis”, ”psychedelics” and “stimulants”, “erotica”, “forgeries” and “fireworks” before making purchases with Bitcoins.

One listing for heroin promised buyers: “All rock, no powder, vacuum sealed and stealth shipping.”

Ulbricht was arrested at a library

Undercover agents made more than 100 purchases of LSD, ecstasy, heroin and other drugs offered on the site, the court papers said.

Services for sale on Silk Road included hacking into accounts at Twitter, Facebook or other social networks and tutorials for cracking cash points.

Guns and hitmen were also on offer in 10 countries on the site, which launched in 2011, according to the charges.

Ulbricht himself is accused of using the murder-for-hire services on Silk Road this year.

The physics graduate allegedly told an undercover investigator posing as a drug dealer he would pay him to “beat up” a former employee he believed had stolen money from Silk Road.

Later Ulbricht wrote to ask whether he could “change the order to execute rather than torture” and agreed to make two payments of $40,000 (£24,000) each to get the job done, according to authorities.

As of July, there were nearly one million registered users of the site from the UK, US, Germany, Russia and elsewhere, the court papers said.

Federal authorities shut the site down and swooped on Ulbricht on Tuesday afternoon in a branch of San Francisco’s public library.

The FBI has closed the site and seized millions in digital currency

Ulbricht was online on his laptop chatting with a co-operating witness about Silk Road when FBI agents took him into custody, authorities said.

Ulbricht did not enter a plea to any of the charges when he appeared in court on Wednesday in San Francisco.

The raid was not the first time the US government has made arrests related to Silk Road.

Earlier this year, authorities in South Carolina arrested Eric Daniel Hughes, who used Silk Road under the name Casey Jones, and charged him in state court with drug possession.