Two security firms have said that the theft of $1.5 billion in cryptocurrency last week was committed by North Korean hackers.

Bybit, a major cryptocurrency exchange, said Friday that hackers stole $1.5 billion in digital currency during a routine transfer of Ethereum, one of the most popular cryptocurrencies, between digital wallets.

Blockchain analytics firm Elliptic on Sunday identified North Korea's Lazarus Group as the perpetrators.

TRM said Friday it was able to "monitor the movement of stolen assets in real time."

"TRM has determined — with high confidence — that the Bybit hack was perpetrated by North Korean hackers. This assessment is based on substantial overlaps observed between addresses controlled by the Bybit hackers and those linked to prior North Korean thefts," TRM said on its website.

Ben Zhou, Bybit's CEO, said on social media Sunday that the firm had replenished its reserves in the wake of the theft, CNBC reported.

North Korean state hackers have been linked to several high-dollar crypto thefts in recent years. In December, the FBI, the Defense Department, and the National Police Agency of Japan issued a joint statement blaming North Korean hackers for the theft of $308 million from a Japanese crypto firm.

Information from The Associated Press was used in this report.

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