The US has warned that Chinese intelligence was using deceptive methods to target current and former US government employees for recruitment, however Beijing rejects such insinuations.

The warning from the National Counterintelligence and Security Center comes amid mass federal firings led by Elon Musk's Department of Government of Efficiency.

"Foreign intelligence entities, particularly those in China, are targeting current and former US government (USG) employees for recruitment by posing as consulting firms, corporate headhunters, think tanks, and other entities on social and professional networking sites," the center said in a bulletin on Tuesday.

The center said deceptive online job offers and other approaches have become more sophisticated in targeting individuals with US government backgrounds seeking new employment. It warned current and former federal employees of such approaches.

It added that clearance holders were obligated to protect classified data even after leaving federal employment.

The Chinese foreign ministry said on Wednesday it was not aware of the situation and accused the US of spying on China.

Ministry spokesperson Lin Jian called the US actions "irresponsible practices" and said it was engaging in "global espionage without any disguise".

Reuters previously reported about a network of companies operated by a secretive Chinese tech firm that had been trying to recruit recently laid-off US government workers.