China on Tuesday returned the United States underwater drone it had seized on December 15, reported the BBC. China’s Defence Ministry confirmed the development, adding that the “handover” process was carried out smoothly “after friendly consultations between the Chinese and US sides”.

A statement from the Pentagon said that US will “fly, sail, and operate in the South China Sea” where international law allows. It added that the incident was inconsistent with international codes of conduct, and it would continue to investigate the matter.

The drone was handed over to US near the location from where it was seized, around 92 km north-west of Subic Bay. The drone was deployed by oceanographic vessel USNS Bowditch northwest of Subic Bay, off the coast of the Philippines. It was part of a program to collect oceanographic data, including the temperature, clarity and salinity of the water.

The seizure had led to deteriorating relations between the two global powers. The US had demanded the immediate release and return of the vessel, in a formal demarche lodged through diplomatic channels. On December 17, US President-elect Donald Trump had said that China could “keep the drone”, following which the state-run media in China accused him of not behaving like a president because of his tweets.

The news of the seizure came a day after China admitted that it had installed weapons systems on the artificial islands it had built on the disputed South China Sea. However, the country’s Ministry of Foreign Affairs said the deployment was part of normal defence process and should not be seen as “militarisation”.

In July, an international tribunal in The Hague had ruled in favour of the Philippines and said Beijing had no legal basis to claim “historic rights” over the South China Sea. The Permanent Court of Arbitration accused the country of breaching the sovereign rights of the Philippines by exploring resources near the Reed Bank. However, China dubbed the verdict “ill-founded”. Beijing has also said that its “territorial sovereignty and marine rights” in the seas will not be affected by the verdict.