BEIJING (REUTERS) - A Chinese naval vessel was conducting routine operations in the Western Pacific at the time of US joint drills with Japan and India, the country's Defence Ministry said on Thursday (June 16), responding to claims that the ship shadowed a US aircraft carrier.

A Chinese observation ship shadowed the US aircraft carrier John C Stennis, its commander said on Wednesday, as it was joining up with warships from Japan and India for drills close to waters Beijing considers its backyard.

"It is understood that a Chinese naval vessel carried out normal navigation and training in relevant waters on (Wednesday)," the defence ministry said on its official microblog, in a one-line response to a question.

The drills came as Japan and the US worry that China is extending its influence in the Western Pacific as it pushes territorial claims in the adjacent South China Sea, where it is expanding and building islands.

China has been angered by what it views as provocative US military patrols close to the islands. The US says the patrols are to protect freedom of navigation.

The Japanese government also said that a separate Chinese naval ship entered its territorial waters on Wednesday. China said it was acting within the law and following the principle of freedom of navigation.