The brief Chinese-language report said the accident occurred recently in Chinese waters east of the Neichangshan islands, which lie between the north-eastern province of Liaoning and North Korea.
The submarine was on an exercise when the accident occurred, and “because of a mechanical malfunction, the 70 crew members on board died”, the Xinhua report said, without providing further details.
The report, which quoted unidentified navy sources, said the vessel, with the hull number 361, has already been towed back to an unidentified port. Military analysts said the hull number appeared to identify it as a Ming-class submarine, often used for patrols and coastal defence.
China’s military, which has a tradition of secrecy, did not comment about the accident but Chinese naval expert Michael McGinty, from the Royal United Services Institute for Defence Studies in London, said the mishap likely happened while the submarine was on the surface.
“If the accident happened when the vessel was underwater, it was less likely that China could have recovered it,” said McGinty, a former British submariner. “For an accident to have been so catastrophic when the submarine was on the surface, I find it a very mysterious thing,” he said.
McGinty said the submarine’s batteries might have leaked acid that mixed with sea water, creating toxic chlorine gas that killed the crew. The torpedoes might have leaked propellant that poisoned the crew, he said.
China began building the Ming-class submarines in the 1970s, and they are obsolete by modern standards, according to the Federation of American Scientists, a respected source of military information. The first three Ming-class subs were completed between 1971 and 1979, and one of them was scrapped after a fire, according to the website of Jane’s Information Group, a leading of source of defence information. China is believed to have more than a dozen Ming-class submarines.
China’s submarine fleet includes 66 boats, most of them ageing diesel-electric vessels, McGinty said. The fleet suffers from a chronic shortage of funding, poor training and insufficient maintenance, he added.
But the Chinese are aggressively updating their fleet with Russian-made Kilo-class diesel-electric submarines.
Xinhua said that former President Jiang Zemin, the chairman of the Central Military Commission, sent condolences to family members.