Reuters news and other sources are reporting that China announced on Thursday that it used a small, manned submarine to plant its national flag deep beneath the South China Sea. Beijing has argued with Washington and Southeast Asian nations over territorial disputes in this area.
The submarine achieved the feat during 17 dives from May to July, when it went as deep as 3,759 metres (12,330 ft) below the South China Sea, the official China News Service said.
China, Brunei, Malaysia, Vietnam, the Philippines and Taiwan all stake claims to territory in the South China Sea, which holds potentially big energy sources and is a major shipping route. All except Brunei have a military presence in the area, and the boundary claims have sparked naval clashes in the past.
The South China Sea holds valuable fishing grounds and as-yet largely unexploited oil and natural gas fields.
China accused the United States of meddling after Secretary of State Hillary Clinton raised the territorial claims in the sea at a regional forum in July, and said Washington backed a multilateral approach to resolving them.
In late July, Chinese naval forces carried out drills in the disputed southern waters.