KUALA LUMPUR (Reuters) - A Chinese submarine has docked in Malaysia, the second such visit to the Southeast Asian country this year, as western powers fret over China’s expanding reach in the South China Sea.

China claims nearly all the South China Sea, through which an estimated $3 trillion in international trade passes each year. Brunei, Malaysia, the Philippines and Taiwan also have claims.

Tensions between China and Malaysia over their overlapping claims, however, appear to have eased after Malaysia agreed in November to buy four Chinese naval vessels and pledged with Beijing to handle South China Sea disputes bilaterally.

The Royal Malaysian Navy confirmed the visit by the Chinese submarine, which docked at the Sepanggar naval base in the state of Sabah in Borneo between Friday and Monday.

RMN chief Admiral Ahmad Kamarulzaman Ahmad Badaruddin said it was standard international procedure to welcome visits by foreign navy vessels, “based on each nation’s request and upon diplomatic clearance”.

“This is part of our efforts to enhance defense diplomacy and strengthening bilateral relations,” he told Reuters.

The submarine was escorted by a surface ship from the PLA Navy and was returning to China after conducting escort missions in the Gulf of Aden, according to defense magazine Jane’s 360, which first reported the submarine’s docking.

In January, a Chinese submarine docked in Sepanggar, only the second confirmed visit of a Chinese submarine to a foreign port, according to state media.

Chinese warships have also been calling at ports in Pakistan, Bangladesh and Myanmar, unnerving regional rival India.