Japan conducted large-scale joint exercises with the United States over nearby waters earlier this month involving a total of 52 aircraft, the Air Self-Defense Force said Thursday, amid intensifying maritime activities by China and Russia in the region.

Including aircraft that flew several times, 20 ASDF fighter jets, 29 fighters and two warplanes of the U.S. Air Force, and a U.S. Navy patrol plane participated in the drills on July 6 as well as Monday and Tuesday over the Sea of Japan, the Pacific and the East China Sea, the ASDF said.

Aimed at enhancing the ASDF's "tactical technique and the capabilities of joint Japan-U.S. actions in response" to armed attacks, the joint drills were carried out following two exercises conducted by the allies in late June, according to the ASDF.

In a related move, patrol planes of Japan's Maritime Self-Defense Force and the U.S. Navy carried out a joint drill on Wednesday over waters near Japan's southwestern islands, the MSDF said.

The drills came as Chinese and Russian warships have been repeatedly spotted off Japan, especially since Russia launched its invasion of Ukraine in late February, though the vessels did not intrude into Japanese territorial waters.

In early July, a Chinese naval ship pursued a Russian warship just outside Japanese territorial waters around the Senkaku Islands in the East China Sea, according to Japan's Defense Ministry, in an apparent attempt to demonstrate Chinese sovereignty over the Tokyo-controlled, Beijing-claimed islets.

Two days later, an information-gathering vessel of the Russian navy briefly entered an area just outside Japan's territorial waters around its southernmost Okinotori Island in the Pacific, according to the ministry.

Beijing and Moscow also flew a total of six strategic bombers over the Sea of Japan, the East China Sea and the Pacific in late May, when Tokyo was hosting a summit of the Quad group, also involving Australia, India and the United States.