Anxious Bitcoin investors in Tokyo have called for legal action against the chief executive of an exchange where hundreds of millions of dollars' worth of the virtual currency appear to have vanished.
Dozens of members of "Bitcoin Tokyo" gathered in a restaurant on Thursday in the Japanese capital, some nursing possible six-figure losses after an apparent grand theft from the digital vaults of the MtGox exchange.
American IT engineer Aaron Gotman said he had 463 bitcoins at MtGox, worth well over $US200,000 ($A223,726).
"What happened at MtGox was first incompetence, but then it could have gone to fraud at the end if they were knowing they didn't have the bitcoins they were selling," he said.
"If that's true, (MtGox CEO Mark) Karpeles should face justice and go to jail," he said.
"Now only a miracle could give me back my bitcoins."
Gotman, 35, is one of a reported one million people who had an account at MtGox, the first exchange for the crypto-currency.
Bitcoin continued its rollercoaster ride Thursday, trading around $US577 at 1330 GMT, according to the Coindesk index, which showed it had been around $US20 lower at one point on Thursday.
The value swing is characteristic of a currency that began life worth a few cents and topped out last year well above $US1000.
The MtGox website, which went dark on Tuesday, remained largely empty, save for a message from Karpeles, the France-born chief executive who has not been seen in public for several days.
"As there is a lot of speculation regarding MtGox and its future, I would like to use this opportunity to reassure everyone that I am still in Japan, and working very hard with the support of different parties to find a solution to our recent issues," he said.
"Furthermore I would like to kindly ask that people refrain from asking questions to our staff: they have been instructed not to give any response or information. Please visit this page for further announcements and updates."
