A Japanese exchange said it would reimburse customers after 58 billion yen (£380 million) in cryptocurrency was stolen in a hack.
The Coincheck exchange said on Friday it had halted sales and withdrawals of the NEM currency after the largest theft involving digital currency.
It later added that it had restricted dealings in most other cryptocurrencies too, but not Bitcoin.
At a Friday night news conference, Coincheck President Koichiro Wada bowed and apologised.
He said the company might seek financial assistance, according to Kyodo News service. Japanese TV footage showed a small group of customers standing outside the company's Tokyo head office on Friday night.
Coincheck, which calls itself the leading Bitcoin and cryptocurrency exchange in Asia, said it detected the unauthorised access to its system about 3 am on Friday.
"We know where the funds were sent," Company chief operating officer...