a signboard of the name of cryptocurrency exchange Coincheck, in Tokyo. Picture: Kyodo News via AP

Tokyo  - Some 6.7 billion yen (59.7 million dollars) in cryptocurrency has been stolen from a Japanese exchange during a hack, the operator said on Thursday.

Osaka-based Tech Bureau said in a statement it had suspended deposits and withdrawals after three types of digital currency disappeared earlier this month. Of the 6.7 billion yen, 4.5 billion came from assets deposited by customers.

The exchange was hacked over a period of about two hours until around 7 pm (1000 GMT) Friday, Tech Bureau said. The company detected an abnormality in the system on Monday and found that the currencies had disappeared the following day, it said.

Tech Bureau has asked for 5 billion yen in assistance from a subsidiary of Fisco, a financial services company.

Coincheck President Koichiro Wada, left, bows in apology at the beginning of a news conference in Tokyo. Japanese media say the Coincheck exchange has lost 58 billion yen ($530 million) in cryptocurrency because of hacking. Picture: Takuya Inaba/Kyodo News via AP

The incident took place despite the government stepping up its supervision of the industry after a 58-billion-yen theft at another cryptocurrency exchange operator Coincheck in January.