Tokyo-based cryptocurrency exchange Coincheck has until February 13 to explain to the Japanese government how hackers stole $530 million worth of digital coins. 

In one of the biggest-ever hacking heists of digital money more than $500 million dollars worth of so-called NEM coins were gone in a flash on Friday in Japan, stolen from Tokyo-based Coincheck.

The crypto-currency exchange was forced to freeze trading on all currencies except bitcoin.

Coincheck promised to repay nearly 90% of what was taken with its own funds.

There will be a payout in yen, not digital coins, to around 260,000 affected customers.

On Monday Tokyo regulators warned Coincheck to get its act together and explain what happened by mid-February. 

The NEM coins were stored in a so called 'hot wallet' instead of a more secure 'cold' one.

Asked why, Coincheck president Koichiro Wada cited staff shortages and technical difficulties.

Crypto currency exchanges in Japan only had to register with the government after April last year.

Companies like Coincheck have been allowed to continue business as normal while waiting for approval.

NEM coins can actually be traced and the NEM Foundation in Singapore says it has a full account of all of Coincheck's lost coins.

However, it also says it has no way to return the stolen funds to their owners and so far the hacker has not moved any of the money to a personal account, or onto another exchange.