Tokyo is watching with "grave concern" the planned joint military drills of China and Russia, local media reported on Wednesday.
Top Japanese government spokesman Hayashi Yoshimasa said that it is difficult to assess the intention and purposes of the joint drills of Beijing and Moscow, Japan's public broadcaster NHK reported.
He added that the two countries also held joint training with naval vessels and bombers recently.
"Japan views the upcoming exercises as part of the two countries' efforts to bolster their military alliance," the broadcaster quoted Hayashi as saying.
On Monday, China said that Russia will participate in an upcoming military exercise that will take place in the Pacific Ocean later this month.
China's statement comes weeks after Japan claimed that a Chinese military spy plane violated its airspace for the first time, reportedly entering Japanese airspace above the waters of the East China Sea, near islands in the southwestern province of Nagasaki.
On Tuesday, Russian and Chinese warships began a major joint naval exercise.
According to a Russian Defense Ministry statement, 400 warships, submarines, and support vessels will participate in the strategic command and staff exercise Ocean-2024.
It said the drills will be conducted across the Pacific and Arctic Oceans, as well as the Mediterranean, Caspian, and Baltic Seas.
Most recently, China and Russia conducted a joint military exercise in the waters and airspace adjacent to Zhanjiang, located in south China's Guangdong Province, back in July.
The joint exercises between China and Russia serve as a notable display of their strategic partnership, with analysts viewing them as a response to the escalating US military presence in the region.
