The Vietnamese government has protested against China's laying of underwater cables between outposts in Vietnam’s Hoang Sa (Paracel) islands.

Chinese ship laying underwater cables in Paracels. Image: Planet Labs

Aerial footage by US-based Planet Labs Inc. has recently shown a Chinese ship laying underwater cables between outposts in Vietnam’s Hoang Sa (Paracel) islands.

Spokesperson Le Thi Thu Hang of Vietnam’s Ministry of Foreign Affairs affirmed that any related parties need to take actions responsibly to avoid complicating the situation in the East Sea (refers to the South China Sea) to contribute to the regional peace maintenance.

“Any activities with respect to the two islands without Vietnam’s permission are all null and void,” Hang said at a regular press conference on June 11, referring to the Hoang Sa (Paracel) and Truong Sa (Spratly).

Experts fear the cables will strengthen Beijing’s ability to detect foreign ships after China established outposts in Paracel and Spratly archipelagos.

Professor James Kraska at the US Naval War College that China may have been strengthening existing encrypted military communications between Chinese outposts and plotting a South Surveillance System (SOSUS) to track submarines, The Express reported.

Bryan Clark, a senior fellow at Washington-based think tank Hudson Institute, said a tracking device between Woody Island and Hainan Island would be an ideal location as it is home to the submarine fleet of the People’s Liberation Army Navy (PLAN).

Detailed images show the vessel laying cables between Tree Island, North Island, and Woody Island – the largest of the Paracels.

Vessel-tracking software revealed the Chinese-flagged Tian Yi Hai Gong ship sailed to the Paracels on May 28 and continued to sail southwest on June 5 and visited three other key military outposts on Drummond island, Yagong island, and Observation Bank.