Unnamed US officials told the Post that hackers took 614 gigabytes of information from the contractor, which was also unnamed.
Chinese state-sponsored hackers breached a U.S. Navy contractor and stole huge amounts of highly sensitive intelligence involving secretive military operations, The Washington Post reported Friday.
The data was reportedly stolen from a Navy contractor who works for the Naval Undersea Warfare Center in Newport, Rhode Island, although the Post's sources would not say which contractor was targeted.
Among the data seized was also information on the US Navy's plans to mount a supersonic anti-ship missile on a submarine, The Post reported.
She said it would be "inappropriate to discuss further details at this time".
While the data was stored on an unclassified network belonging to the contractor, it is considered highly sensitive due to the nature of the technology under development and the links to military projects.
Data stolen in the breach include plans for a supersonic missile project, U.S. officials told the Washington Post.
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Republicans have pointed to the revelation as proof that the Obama administration was "desperate" for the Iran deal. Rob Portman, the chair of the Permanent Subcommittee on Investigations, said in a statement.
China has also stepped up pressure on its neighbour Taiwan, prompting USA nuclear bombers to swoop on the South China Sea. USA officials have always been anxious that ZTE equipment could be used by the Chinese government for espionage or sabotage.
'They are completely focused on getting advanced weapons technology through all kinds of means.
Much of the stolen material was linked to a secret project called Sea Dragon and included signals and sensor data, and submarine radio room information relating to cryptographic systems, according to the newspaper.
According to the Post, the Sea Dragon project was created by the Pentagon in 2012 to adapt existing US military technologies to new applications.
The Chinese government has made long-term investments in bolstering its military capabilities over the years, acquiring quieter submarines equipped with sophisticated weaponry.
Pentagon officials would not name the government contractor.