LONDON (Reuters) - British police have arrested four men suspected of being significant users of Silk Road, the anonymous Internet marketplace used to buy illegal drugs and criminal services that was shut down by U.S. authorities last week.
The new National Crime Agency (NCA) said on Tuesday the four suspected drug offenders were detained hours after the U.S. Federal Bureau of Investigation arrested Ross Ulbricht, the suspected creator of Silk Road also known as "Dread Pirate Roberts".
The NCA, which became operational on Monday, warned there would be more arrests related to Silk Road in coming weeks.
It said it would spearhead a campaign against virtual currencies that pose a potential criminal threat to Britain, such as bitcoins.
These were used by Silk Road customers to buy and sell illegal goods and services, according to the FBI, which seized $3.6 million (2.2 million pounds) worth of the currency in its raid on Silk Road.
"This is only the start of a wider campaign for the NCA to tackle the 'dark' or 'deep' web and the criminals exploiting it," Andy Archibald, head of the agency's National Cyber Crime Unit, said in a statement.
He was referring to areas of the Internet such as Silk Road that are not readily accessible via standard search engines.
"These criminal areas of the Internet aren't just selling drugs; it's where fraud takes place, where the trafficking of people and goods is discussed, where child abuse images are exchanged and firearms are traded," said Archibald.
The NCA said it had worked closely with U.S. law enforcers to identify the four suspects who were arrested last week.
One is a man in his early 50s from Devon in southwest England, while the other three are in their early 20s and are from Manchester in northwest England.
Keith Bristow, director general of the NCA, said it was impossible for criminals to completely erase their digital footprints no matter how technology-savvy they were.
"The hidden Internet isn't hidden and your anonymous activity isn't anonymous. We know where you are, what you are doing and we will catch you," he said in the NCA statement.
Bristow said hidden or anonymous online environments were a key priority for the NCA, which had 4,000 officers and the latest technology at its disposal to tackle the problem.
The NCA, intended as a one-stop-shop agency responsible for the fight against serious and organised crime in Britain, has been likened to the FBI. Its creation was announced in 2011 and it was launched on Monday.
Reporting by Estelle Shirbon; editing by Tom Pfeiffer