President-elect Donald Trump has hit out at China once again on Twitter over the seizure of a US Navy drone, telling them to "keep it".

A Chinese warship this week seized the US Navy drone in the South China Sea, prompting concern that China's militarisation of the South China Sea and the US response to it could escalate into something worse than diplomatic rhetoric.

And Trump continued to risk damaging US relations with China after initial tweets about the situation, writing: "We should tell China that we don't want the drone they stole back — let them keep it!"

In an earlier Tweet, Trump had been mocked for misspelling a tweet about the situation, writing: "China steals United States Navy research drone in international waters — rips it out of water and takes it to China in unpresidented act."

The message was later re-written with the correct spelling and the original tweet deleted, but not before it had been widely shared on social media.

In a statement to Reuters, China's foreign ministry said the issue was being resolved, and suggested the US' "hyping up" of the issue had been detrimental.

"China decided to return it to the US side in an appropriate manner, and China and the US have all along been in communication about it," the statement read.

"During this process, the US side's unilateral and open hyping up is inappropriate, and is not beneficial to the smooth resolution of this issue. We express regret at this."

The drone was in international waters 92km (57 miles) north-west of the Philippines being guided by oceanographic survey ship, USNS Bowditch when a Chinese warship scooped it from the water.

No shots were fired in the incident, but the US says the drone's markings clearly stated it was American property and that should not be removed from waters, and the Chinese had no right to take it.

However, there is concern Trump's comments are making an already tense situation worse.

During his election campaign, Trump was criticised for making inflammatory comments on social media, with pundits questioning whether he would continue to do so if elected, although thus far, the president-elect has not showed any sign of relenting in his provocative tweets.