China deployed a reconnaissance aircraft over Pacific waters east of Taiwan last week that Chinese media said monitored and gathered intelligence on an exercise involving the navies of the United States, Japan, France and Canada.

A Y-9 cargo plane variant fitted with intelligence-gathering equipment most likely monitored and collected intelligence on the exercise, China's state-backed Global Times newspaper reported on Sunday, citing analysts.

Two U.S. aircraft carriers, the USS Nimitz and USS Ronald Reagan, had been operating around the geopolitically important Ryukyu Islands in the Philippine Sea since Thursday, the Global Times cited a Beijing-based think tank as saying.

The islands separate the East China Sea from the Philippine Sea, and dot the West Pacific between Japan and Taiwan, which China claims as its territory.

On Friday, the U.S. began the exercise in the Philippine Sea with two carrier strike groups jointly operating for the first time since June 2020, the U.S. 7th Fleet said in a statement.

The Japanese defence ministry reported a sighting of a Y-9 reconnaissance variant in the Pacific on Thursday.

A spokesperson for the Japanese ministry said on Monday it was analysing a piece of equipment attached to the undercarriage of the Y-9 variant that had not been seen before.

Military encounters between China and the United States and its allies in the Western Pacific have risen in recent years as China has grown increasingly assertive in the East and South China Seas, as well as around Taiwan.

Days before the quadrilateral exercise, the coast guards of the Philippines, United States and Japan held their first trilateral exercise off the coast of a western Philippine province.