Satellite images from the Planet Labs observation company, dated August 18, appear to capture a Type 093 nuclear attack submarine at the entrance to a tunnel at Yulin Naval Base, located in southern Hainan Island and considered by military experts to be China’s most important base. from the South China Sea.

Drew Thompson, a former U.S. Department of Defense official and researcher at the University of Singapore, said it was a rare incident.

“It is unusual for a commercial satellite to be above it at the right time,” on a clear day, he said. On the other hand, the existence of an underground military base is not unusual for China, as a large number of military equipment is housed in these bases, from submarines to missile systems, Thompson pointed out.

“The Chinese have a formidable experience in building underground facilities. It is in step with their strategic culture. They have a deep-rooted sense of vulnerability to attacks on their coast. “

Yulin Base, located at the southern end of Hainan Island, 470 kilometers southwest of Hong Kong, is one of China’s key strategic facilities. The presence of the submarine at this base does not send a particular signal, says the expert, but only reflects the consolidation of China’s growing submarine fleet – which is protected and protected from the eyes of the world in these underground bases.

A U.S. Navy spokesman confirmed to CNN that the United States has sent U.S. P-8A Poseidon intelligence reconnaissance aircraft near Yulin base at least once this year.

Carl Schuster, a former chief operating officer at the Pacific Joint Intelligence Center, explained that underground bases make intelligence work more difficult.

“We have no evidence of submarine combat readiness, operational response times and availability. The tunnels can obscure potential opponents’ submarine status and operational patterns, rendering them unable to determine the level of Chinese military training – critical information for assessing China’s intentions and plans, “he said.

According to the non-profit Nuclear Threat initiative, China would own six Type 093 nuclear submarines – they could launch torpedoes and cruise missiles.