A ransomware attack on the Industrial and Commercial Bank of China has disrupted the US Treasury market, according to market participants.

The Securities Industry and Financial Markets Association told members on Thursday that ICBC, China’s largest bank, had been hit by ransomware software, which paralyzes computer systems unless a payment is made, according to several people familiar with the discussions.

The attack prevented ICBC from settling Treasury trades on behalf of other market participants, according to traders and banks.

ICBC was starting to restore services as of Thursday afternoon, according to some of the people briefed on the incident. ICBC did not respond to a request for comment.

“We are aware of the cybersecurity issue and are in regular contact with key financial sector participants, in addition to federal regulators. We continue to monitor the situation,” a Treasury spokesperson said in a response to a question about the FT report.