The US Justice Department on Monday accused the hackers of stealing the sensitive personal information on some 145 million Americans, in one of the world's largest-ever data breaches.

China rejected the claims on Tuesday.

"The Chinese government and army... never engage in or participate in activities of trade theft through the internet," said foreign ministry spokesman Geng Shuang at a regular press briefing.

He said that China has "always resolutely opposed and cracked down on all forms of online hacking attacks" and is a "staunch defender of cybersecurity".

"China is also a serious victim of US cybertheft," Geng said.

The four members of the People's Liberation Army's 54th Research Institute -- Wu Zhiyong, Wang Qian, Xu Ke and Liu Lei -- were charged with multiple counts of hacking, computer fraud, economic espionage and wire fraud.

Attorney General Bill Barr said it was a "deliberate and sweeping intrusion into the private information of the American people".

Investigators said the Chinese military unit, using encrypted channels, ran some 9,000 queries through Equifax's computing systems to obtain, divide, compress and exfiltrate the data, bit by bit.

The US believes the suspects are currently in China.