Japan's Defense Ministry says Chinese and Russian bombers jointly flew over areas around Japan on Tuesday.
The ministry says six bombers made a long flight over the Sea of Japan, the East China Sea and the Pacific Ocean near Japan.
It says they consisted of two each from China and Russia, and another two believed to be Chinese. It also says a Russian intelligence aircraft was confirmed.
Japan's Air Self-Defense Force scrambled its fighters in response to the flight. It says there was no violation of Japan's airspace.
On Tuesday, Japan hosted a "Quad" summit with the United States, Australia and India in Tokyo to seek cooperation in the Indo-Pacific region.
Japan's Defense Ministry expressed serious concern about the flight to China and Russia through diplomatic channels.
It was the fourth time that the ministry announced a joint flight by Chinese and Russian military planes around Japan, and the first since last November.
From Sunday to Monday, two Chinese frigates passed through the Tsushima Strait off southwestern Japan. On Monday, a Chinese missile destroyer sailed between Okinawa's main island and Miyako Island before heading out to the Pacific Ocean.