Beijing on Monday accused the United States of launching "tens of thousands" of cyberattacks on China and pilfering troves of sensitive data, including from a public research university.
Washington has accused Beijing of cyberattacks against U.S. businesses and government agencies, one of the issues over which ties between the two powers have nosedived in recent years.
China has consistently denied the claims and in turn lashed out against alleged U.S. cyber espionage but has rarely made public disclosures of specific attacks.
But a report released Monday by its National Computer Virus Emergency Response Center (CVERC) accused the U.S. National Security Agency (NSA) of carrying out "tens of thousands of malicious attacks on network targets in China in recent years."
It specifically accused the NSA's Office of Tailored Access Operations (TAO) of infiltrating the Northwestern Polytechnical University in the city of Xi'an.
The university is funded by China's Ministry of Industry and Information Technology and specializes in aeronautical and space research.
CVERC alleged that TAO infiltrated the university's networks and took "control of tens of thousands of network devices" including servers, routers and network switches.
Using dozens of cyber weapons and exploiting previously unknown flaws in the SunOS operating system, the unit gained access to "core technical data" including passwords and the operations of key network devices, the report said.
TAO has "stolen over 140 gigabytes of high-value data" in recent years and received assistance from groups in Europe and South Asia, CVERC said in the report, which was co-authored by the private Chinese cybersecurity firm Qihoo 360.
The Foreign Ministry in Beijing on Monday condemned the alleged hack, saying it "seriously endangers China's national security and users' personal data security."
"We ask the U.S. to provide an explanation and urge them to stop immediately this illegal move," Mao Ning, a spokesperson for the Foreign Ministry, said at a regular press conference.
The NSA did not immediately respond to an Agence France-Presse (AFP) request for comment.
In June, Xi'an authorities said they had launched an investigation into a reported cyberattack at Northwestern Polytechnical University that carried the hallmarks of "overseas hacking groups and unlawful elements."
The attacks "caused significant risks and hidden dangers for normal work and life at our school," a university cybersecurity official told state broadcaster CCTV in comments published on Monday.
Last year, Washington accused Beijing of carrying out a massive attack on Microsoft's email software that affected at least 30,000 US organizations -- including local governments – as well as customers in other countries.
China denied the allegations and countered that Washington was the "world champion" of cyber espionage.