A major cryptocurrency exchange says it was the victim of a sophisticated hack that stole about $1.5 billion worth of digital currency, marking one of the biggest online thefts of all time.

Bybit that a routine transfer of Ethereum, one of the most popular cryptocurrencies, between digital wallets was 鈥渕anipulated鈥� by an attacker who transferred the crypto to an unidentified address.

The company sought to reassure customers that their cryptocurrency holdings with the exchange were safe. The company added that news of the hack had led to a surge in withdrawal requests and there could be delays in processing them.

Ben Zhou, Bybit's CEO, that his company would remain solvent even if the hacked crypto wasn't recovered.

鈥淲e can cover the loss,鈥� he said.

Stealing cryptocurrencies is a favorite tactic of hackers. North Korean state hackers, in particular, have been linked to several high-dollar crypto thefts in recent years. In December, the FBI, the Defense Department and 春色直播 Police Agency of Japan issued a blaming North Korean hackers for the theft of $308 million from a Japanese crypto firm.