The Justice Department and the FBI said on Wednesday that they seized two Chinese state-sponsored online platforms that targeted US critical infrastructure and other critical networks, including Nasa, the Federal Reserve and the US Senate.

According to court documents, the seizures involved a group known as “QTFY”, operated by China-based Nanjing Xinjiuwei Network Technology Co, which created and ran the QScan and QTRouter sites.

“State-sponsored malicious hackers preying on America’s critical infrastructure will be stopped and prosecuted,” said US Attorney General Todd Blanche in a statement. “Federal law enforcement investigated and disabled [China’s] malicious software, the latest in a series of technical operations to dismantle indiscriminate hacking activities sponsored by the People’s Republic of China [PRC].”

QTFY allegedly offered computer hacking services for a fee to its clients, including China’s Ministry of State Security (MSS) and the People’s Liberation Army, according to court documents in the Southern District of California.

The Chinese embassy in Washington said the Chinese government opposes and combats all forms of cyberattacks. “We urge the US side to stop using cybersecurity issues to smear or discredit China,” the spokesman said.

Other reported victims of the QTFY hacking operations included the Department of Energy, Department of Justice, Department of Health and Human Services and the National Institutes of Health as well as hospitals, telecommunications providers, power companies, financial institutions and defence contractors.