Four men have been arrested in Britain over the online narcotics bazaar Silk Road.
Britain's newly created National Crime Agency (NCA) said the men were arrested last week just hours after the founder of the infamous website, 29-year-old Ross William Ulbricht - also known by his online nickname "Dread Pirate Roberts" - was arrested in the US.
Other British suspects are likely to be held in the coming weeks, the NCA added.
The agency said it was investigating four men, one in his early fifties from Devon in southwest England, and the others in their early twenties from Manchester in northwest England.
All four were arrested on suspicion of supplying controlled drugs and had been bailed to a later date, a spokeswoman said.
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"These arrests send a clear message to criminals - the hidden internet isn't hidden and your anonymous activity isn't anonymous," said NCA director general Keith Bristow.
"It is impossible for criminals to completely erase their digital footprint.
"These latest arrests are just the start - there are many more to come."
US federal agents shut down the Silk Road - which used sophisticated privacy-protection technology to let users pay for drugs, hitmen, hacker tools and forged documents - in a bust last week.
Prosecutors say the website has been used by thousands of drug dealers to distribute hundreds of kilograms of heroine, cocaine and other drugs, in transactions worth more than $US1.2 billion ($A1.28 billion).
The NCA, dubbed Britain's equivalent of the FBI, was launched on Monday.
Its 4500 officers are tasked with targeting the estimated 37,000 people involved in serious and organised crime in Britain.
