China’s ICBC Bank, the world’s largest bank by assets, has paid a ransom to cybercriminals who hacked the computer system of the US unit of the financial institution last week, a spokesman for the Lockbit ransomware group said in a statement cited by Reuters and news.ro.

The news agency could not independently verify.

The US arm of the bank was hit by a ransomware attack that disrupted trading in the US Treasury market last Thursday.

“They paid the ransom, the deal is done,” a Lockbit representative told Reuters via Tox, an online messaging app.

A cyber attack on Chinese bank ICBC left its U.S. unit temporarily owing Bank of New York Mellon $9 billion due to pending transactions, prompting the parent company to pour significant capital into the unit to settle the transactions, sources familiar with the matter said, Reuters cited as saying.

BNY Mellon later received its money, the sources said.

The attack, confirmed by ICBC on Thursday, is the latest in a series of ransom demands by hackers this year.

ICBC Financial Services, the U.S. arm of the Chinese bank, said on Thursday it was investigating an attack that knocked out some of its systems and was moving toward recovery.

ICBC officials told market participants on a call hosted by industry group the Securities Industry and Financial Markets Association (SIFMA) on Friday that it had hired a third party to help secure its systems, sources said.

ICBC did not immediately respond to a request for comment.