A senior U.S. official confirmed on Thursday that China's latest nuclear-powered attack sub sank in the first half of this year. This could be an embarrassment to Beijing, which is seeking to increase its military capabilities.

China has already built the largest fleet in the world with more than 370 ships. It has also begun production of a brand new generation of nuclear submarines.

Unnamed senior U.S. officials said that China's first-in class nuclear-powered attack sub sank near a pier between May and June.

Officials said that it was unclear what caused the ship to sink, or if it had nuclear fuel aboard at the time.

The official, using the acronym of the People's Liberation Army, said that the incident raised deeper questions about internal accountability and oversight in China's defense industries, which have long been plagued with corruption.

The official said, "It is not surprising that PLA Navy would attempt to conceal" the sinking.

The Chinese embassy in Washington has not responded to an immediate request for comment. The Wall Street Journal was the first to report this news.

Satellite images taken by Planet Labs in June show cranes on the Wuchang Shipyard where the submarine was docked.

According to a Pentagon report, China will have six nuclear-powered ballistic-missile submarines by 2022. It will also have six nuclear powered attack submarines as well as 48 diesel-powered assault submarines. The U.S. Defense Department said that this submarine force will grow to 65 ships by 2025, and to 80 ships by 2035.

China announced on Wednesday that it successfully launched an intercontinental missile into the Pacific Ocean. This move is likely to cause international concern about China's nuclear buildup.

In an effort to avoid miscommunications and stabilize military relations, the United States and China met at the theater level commander level for the first ever earlier this month. This was in response to regional hotspots such as the South China Sea. (Reporting and editing by Jonathan Oatis and Idrees Stewart; Additional reporting and editing by David Brunnstrom, Jonathan Landay and David Brunnstrom)

(source: Reuters)