Two senior Chinese naval officers have been demoted after an investigation showed operational errors were to blame for the deaths of 70 sailors on a navy submarine on May 2.

The move followed the release in Beijing on Friday of the results of an investigation into the accident on Submarine No 361 of the Chinese People's Liberation Army navy.

Ding Yiping, commander of the North China Sea (Beihai) Fleet, and Chen Xianfeng, political commissary of the Beihai Fleet, were demoted after China's Central Military Commission found them to have been responsible for the accident, which was caused by improper direction of the vessel's operations.

Eight other officers with some responsibility for the accident were either dismissed or demoted.

All 70 sailors on board the submarine died east of the Neichangshan Islands off East China's Shandong Province.