China on Friday hit out at accusations from Washington that its hackers were behind a massive breach of confidential U.S. government employee data security.
State-run Xinhua news agency, an official mouthpiece for the ruling Chinese Communist Party, called the accusations "irresponsible and counterproductive," accusing the Department of Homeland Security of "jumping to conclusions and making hypothetical accusations."
So far, no evidence had emerged to support the claim, made by Sen. Susan Collins of the Senate Intelligence Committee, it said.
Collins told reporters that the sophisticated nature of the attack "points to a nation state" as the originator.
"We're still evaluating how serious the breach is, but if it does involve the compromising of the personal records of four million Americans, I certainly think that a strong response is warranted," Collins said.
Xinhua said the allegation was another example of Washington's "habitual slander" against Beijing on cyber security.
"Jumping to conclusions and making hypothetical accusations is irresponsible and counterproductive," Xinhua quoted the Chinese ambassador to the U.S., Zhu Haiquan, as saying.
It said Washington was guilty of "applying double standards" on cyber espionage in the wake of revelations by former National Security Agency (NSA) contractor Edward Snowden.
"The U.S. government and relevant departments have long been engaged in large-scale, organized cyber theft, wiretapping and supervision of political figures, enterprises and individuals of other countries, including China," the agency said.
Millions at risk
The massive hacker attack broke into U.S. government computers, potentially compromising confidential personnel files on four million current and former federal employees, U.S. officials said on Thursday.
The Office of Personnel Management (OPM), which holds employee details and records of security clearances, was targeted in the latest in a string of high-profile security breaches, many of which researchers have claimed originated in China.
U.S. investigators are looking into a possible China connection, Reuters quoted a U.S. law enforcement source as saying.
Official news sites on China's tightly controlled Internet ran the story, referencing overseas news organizations like The Washington Post and Reuters.
Far from denying the attack came from China, comments on the story on major web portal Sina's technology news site were largely positive on Friday.
"Good, good, good, brings a warm glow to the heart," wrote commenter @relieved407 from the eastern province of Anhui on Friday.
"Great! The smart guys outsmarted. An eye for an eye. These are all good ripostes to Uncle Sam," wrote user @halfdayeclipse from Hohhot.
"Just reading, trying to keep a straight face," @eastliprincezhuang added.
And user @thefutureisherewithme from Hubei quipped: "Who knew China was so omnipotent ... turns out they've been secretly turning into a superpower this whole time. Hahahahahaha."
State involvement seen
According to security experts, the attack on OPM and earlier attacks on healt-care providers Anthem and Premera Blue Cross appear to have been carried out on behalf of a state, rather than criminals, it said.
Investigators investigating "malicious activity" on OPM computer systems concluded that the security breach had occurred at the end of May, according to the Department of Homeland Security.
The department said last year that hackers based in China, though not necessarily linked to the Chinese government, had breached the OPM network in an earlier attack.
The FBI said in a statement it is working with other agencies to investigate the latest breach further.
"We take all potential threats to public and private sector systems seriously, and will continue to investigate and hold accountable those who pose a threat in cyberspace," the bureau said in a statement.
A foreign ministry spokesman in Beijing said the accusations were "unscientific," however.
"Always saying that 'it's possible' without fully investigating is irresponsible and unscientific," spokesman Hong Lei told a regular news briefing in Beijing.