Hackers stole more than 20 billion won ($15 million) worth of cryptocurrencies from GDAC, a South Korean crypto exchange, the company said Monday.

The attack occurred at around 7 a.m. Sunday, resulting in the transfer of digital assets, including over 60 bitcoins and 350 Ethereum tokens, to unidentified wallets.

The stolen cryptocurrencies were valued at 20.27 billion won, accounting for about 23 percent of total assets under GDAC's custody.

GDAC said some of the assets appear to have been sent to foreign crypto exchanges. It is cooperating with domestic and foreign crypto exchanges and issuers to block the stolen coins from being laundered, and retrieve them, officials said.

GDAC has reported the incident to the police and the Korea Internet & Security Agency as well as the Korea Financial Intelligence Unit.

Deposit and withdrawal services on GDAC have been suspended, the exchange said, adding it is unclear when the services will resume. (Yonhap)