South China Sea

Tensions in the region have increased recently, with China and the US trading accusations over military activity.

Several nations claim territory in the resource-rich South China Sea.

A military official quoted by the Associated Press news agency said the US pilot was forced to descend about 200ft to avoid a collision.

The defence department said it was addressing the issue through military and diplomatic channels.

Adm. Scott Swift joined the surveillance mission on board a P-8A Poseidon plane on Saturday to witness the aircraft's full range of capabilities, the U.S. Pacific Fleet said Sunday.

The Navy has acquired and plans to purchase more of the versatile aircraft to replace its aging P-3 Orion fleet. The plane can be used for a range of undertakings, including anti-submarine warfare, and surveillance and reconnaissance missions.

A Japanese surveillance plane and about 20 troops conducted the first of two days of joint training with the Philippine navy on Tuesday off the coast of Palawan, a strategically important island not far from contested islands claimed by several countries including China and the Philippines.

While the P-3C plane was being used for maritime search-and-rescue drills and disaster relief drills, the aircraft is also a mainstay of Japan's anti-submarine and other aerial surveillance efforts. In theory, it could help the U.S. keep an eye on the Chinese navy in the South China Sea.