Binance, the world's biggest crypto exchange, has been hit by a hack worth $6.3bn (£4.7bn). The source describes it as thought to be the biggest hack in history.
Binance said half of the affected assets have been frozen. It said many remain in the hands of the hackers. The company later said it has "begun recovering" some funds.
Two analytics firms have attributed the incident to a North Korean hacking unit. No one has claimed responsibility. Binance did not directly respond to questions about possible links to North Korea.
BBC cyber correspondent Joe Tidy explains more about the hack and what affected users should do.