China returns seized US Navy underwater drone after 'friendly consultations'

American authorities say they will continue to investigate incident

USNS Bowditch was recovering two drones last Thursday when a Chinese navy ship approached and sent out a small boat that took one of them, the Pentagon said (AP)

China has handed back an American underwater drone it seized from international waters in the contentious South China Sea.

Beijing’s defence ministry said it returned the unmanned vehicle after “friendly consultations”.

The drone was given back close to where it was taken, around 92km north-west of Subic Bay in the Philippines, Pentagon press secretary Peter Cook said.

Civilian contractors were using the drone to collect unclassified scientific data in international waters, according to the US.

Officials say a non-combat ship was recovering two drones when a Chinese boat approached, launched a small boat and picked up one of them.

Mr Cook said the US would continue to investigate the event, which happened on Thursday near the Philippines.

The incident was one of the most serious confrontations between the superpowers in decades and further escalated tensions between the countries.

Beijing had been angered by President-elect Donald Trump’s public questioning of the One China Policy and by the future leader’s willingness to take a phone call from Taiwanese President Tsai Ing-wen earlier in December.

The seizure has added to US concerns about China's growing military presence and aggressive posture in the disputed South China Sea, including its militarisation of maritime outposts.

In a brief statement, China's Defence Ministry said the drone had been given back to the United States.

"After friendly consultations between the Chinese and US sides, the handover work for the US underwater drone was smoothly completed in relevant waters in the South China Sea at midday on 20 December," the ministry said in a short statement.

The ministry did not immediately respond to a request for more details about the handover.

The US Navy has about 130 such underwater drones, made by Teledyne Webb, each weighing about 60kg and able to stay underwater for up to five months.

They collect unclassified data about oceans, including temperature and depth and are used around the world, but it is unclear how many are used in the South China Sea.

China is deeply suspicious of any US military activities in the resource-rich waters, with state media and experts saying the use of the drone was likely part of US surveillance efforts in the disputed waterway.

Beijing regards Taiwan as a breakaway province that is actually part of China, and the US has essentially accepted this situation for decades while selling arms to Taiwan.

Tensions between China and the US have escalated in recent years as the former has staked claims to ever-increasing chunks of territory and the latter has sought to maintain a strong military presence in the region.

The incident took place inside the Philippines’ exclusive economic zone, and the country described the incident as “very troubling” and increased the likelihood of “miscalculations that could lead to open confrontation.”