Hackers have stolen some $600m (£433m) in what appears to be one the largest cryptocurrency heists ever.
Blockchain site Poly Network said hackers had exploited a vulnerability in its system and taken thousands of digital tokens such as Ether, BBC reported.
In scale, the hack is on par with huge recent breaches at exchanges such as Coincheck and Mt Gox.
In its letter Poly Network said: "The amount of money you have hacked is one of the biggest in defi [decentralised finance] history.
"Law enforcement in any country will regard this as a major economic crime and you will be pursued.
"The money you stole are [sic] from tens of thousands of crypto community members, hence the people."