China seized a submarine probe dropped by an American military aircraft in the South China Sea, according to a social media site linked with state media.

The US aircraft were recently spotted flying over the disputed waters and dropped “unidentified items” into the sea, Yuyuan Tantian said.

China’s coastguard retrieved and inspected an object, footage on the account apparently showed.

China’s coastguard recovered a US submarine probe from the South China Sea, according to a social media site linked to state media. (AP)

It was accompanied by a statement explaining its significance.

“The probe can be used to detect Chinese submarine signals and to counter signals from submarines underwater,” text on the video said, quoting an expert.

China claims virtually the entire South China Sea, but the Philippines, Vietnam, Malaysia, Brunei and Taiwan have also pressed their separate claims.

The three-million-square-kilometres waterway is vital to international trade, with an estimated third of global shipping worth trillions of dollars passing through each year.

China accused of ‘piracy’ after boats rammed, guns stolen in disputed sea
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The United States, supported by allies including Australia, support freedom of navigation through the sea. Their militaries hold regular naval drills in the region to the ire of Beijing.

Earlier this month, the Chinese coastguard clashed with Philippines naval personnel in the South China Sea.

The Philippines military said the military interception by Chinese vessels left two of its ships damaged and sailors injured, including one who lost a thumb.

After a scuffle and repeated collisions, the Chinese seized the boats and damaged them with machetes, knives and hammers.