Nobuhirokubo, Michael Martina, and Hyonhee Shi

(Reuters) –Russian and Chinese military aircraft conducted joint exercises in the Asia-Pacific area to patrol, Russia’s defense ministry stated on Tuesday. This was in a sharp farewell to U.S. president Joe Biden, who had just returned from an Asia trip that ranked Beijing.

In a statement by the defense ministry, they said that the 13-hour-long joint patrol took place over East and Japanese seas. It involved Russian Tu-95 strategic aircraft bombers as well Chinese Xian H-6 fighter jets.

The Japanese defense minister called it a provocation, but a U.S. official claimed that the exercise revealed how deep the cooperation between the countries.

Russian Ministry said that the Russian military had sent planes to shadow the Russian and Chinese fighter jets during the exercises.

Japan scrambled planes to repel Russian and Chinese warplanes from its airspace as Tokyo was host to the Quad Group of countries, Defense Minister Nobuo Kishi said.

Kishi at a news conference stated that Tokyo has conveyed “grave worries” to Russia as well as China via diplomatic channels.

The incident was described by him as an improbable provocation from Beijing and Moscow at a time when Biden and Narendra Modi, the Indian Prime Minister, and Australia’s new leader, Anthony Albanese were in Tokyo.

He said that “we believe the fact this action was taken at the Quad summit makes them more provocative than ever before,” and added it was the fourth incident like it since November.

China’s defense ministry has confirmed that the Chinese military conducted a joint aerial patrol in the Sea of Japan and East China Sea, and it was part of an annual military exercise.

This is China’s first military joint exercise with Russia since Moscow invaded Ukraine on February 24, according to a U.S. Official. And it happened at the end of Biden’s trip.

Senior U.S. officials said that a joint exercise in strategic bomber warfare shows how deep the alignment is.

According to the official, “We believe it indicates that China continues be open to close alignment themselves with Russia via military cooperation.” He also stated that these actions should be planned in advance.

China isn’t abandoning Russia. The official stated that China was ready to support Russia’s east, while Russia is fighting in the west.

Biden said Monday that he would use force to defend Taiwan. But, Biden later claimed that U.S. policies toward Taiwan have not changed. China regards Taiwan as an inalienable piece of its territory and should reunite it with the mainland.

Tuesday’s intrusion was the first since Yoon Suk-yeol, South Korean president, took office May 10. Yoon concluded his meeting with Biden on Sunday. The two leaders pledged their support for countering China’s influence in the region and criticised Russia’s war against Ukraine.

South Korea’s military stated that it had scrambled fighter planes following at least four Chinese warplanes and four Russians entering its air defense area.

The Russian and Chinese aircraft entered and left the Korea Air Defence Identification Zone (Korea ADIZ) in the Sea of Japan, known in Korea as the East Sea, several times through the day, according to South Korea’s Joint Chiefs of Staff.

It stated that the aircraft which consisted of fighter jets as well as bombers, didn’t violate South Korea’s airspace.

According to a Seoul military source, South Korea was not aware of any drills. The source claimed that Seoul alerted Russian and Chinese officials when the aircraft was heading toward its defense zone.

China replied that this was an ongoing exercise. Russia did not respond.

A zone of air defense identification is different from airspace. This area allows countries to unilaterally require that any foreign aircraft identify themselves. No international laws are applicable.