U.S. submarines in the Western Pacific are not immune from surveillance, according to a Hong Kong newspaper. File Photo by Yonhap/EPA
Jan. 23 (UPI) -- Chinese acoustic sensors may be picking up signals between U.S. submarines in the South China Sea and their command base, according to military experts familiar with the technology.
The deployment of surveillance began in 2016, but its use in the high seas was not disclosed until this month, the South China Morning Post reported.
The Chinese government has stated the sensors have a listening range of 620 miles and are being used to analyze earthquakes, weather patterns and wildlife.
But experts who spoke to the Post said they can also be used to intercept underwater signals.
China has installed two acoustic sensors at key locations: the Challenger Deep of the Mariana Trench, and at a point near Yap, an island in the Federated States of Micronesia.
Both locations are less than 400 miles away from Guam, where the United States retains its biggest military base in the Western Pacific.
The technology could be picking up on submarine communications, said an unnamed Chinese military expert.
Surveillance at sea has also targeted Chinese activities.
The Asahi Shimbun reported Tuesday Japan's maritime self-defense forces deployed a P3C patrol vessel near Shanghai and began stopping ships at sea.
The Japanese government said its vessels are working near Chinese territory after finding evidence North Korea was evading sanctions, according to the report.
The report also stated Japan has stepped up maritime surveillance activities at the request of the United States and is monitoring waters around the Korean peninsula, as well as the East China Sea.
Japan's military had picked up on the activities of a vessel sailing under the flag of the Dominican Republic.
Japanese officials told Kyodo News it is likely the boat belongs to a Chinese firm trading petroleum products illegally.