A Japanese cryptocurrency operator has revealed that hackers accessed its systems on on September 14 and stole about $US60 million ($A83 million).
Tech Bureau Corp said in a statement that the unauthorised breach from abroad took place for two hours last week but was only detected on Monday and the damage not discovered until Tuesday.
Assets of the firm's clients made up about 67 per cent of what was stolen, while the rest were funds of a cryptocurrency exchange company integrated with Tech Bureau.
The theft affected three cryptocurrencies, but 89 per cent was in bitcoins and the rest in the virtual currencies MonaCoin (MONA) and Bitcoin Cash (BCH), in amounts not yet accurately calculated, since the investigation is still underway.
The company said that the server is being thoroughly reviewed to prevent further damage, adding that it has requested financial assistance from one of its subsidiaries to cover the damage caused.
The damage suffered by this firm is less than a similar incident in January, when the Japanese operator Coincheck said its system was hacked and some $US534 million were stolen.
The incidents have forced Japanese authorities to tighten controls on the cryptocurrency markets.
