Russian and Chinese bombers conducted another joint patrol between South Korea and Japan

• Russian and Chinese aircraft conducted an exercise over the East China Sea and Sea of Japan on Tuesday, prompting responses from South Korea and Japan.
• It appears to be the first such joint exercise since July 2019, when South Korean aircraft fired hundreds of warning shots and Russian aircraft flying near a group of islets that Seoul and Tokyo both claim.

A year and a half after Russia and China's first joint aerial patrol over the Sea of Japan and East China Sea, Russian and Chinese bombers carried out another joint patrol in the area.

South Korea said Tuesday that it had scrambled fighter jets in response to an intrusion by 19 Russian and Chinese military aircraft.

Four Chinese aircraft entered the Korea Air Defence Identification Zone (KADIZ) followed by 15 Russian aircraft, South Korea's Joint Chiefs of Staff said.

"This incident seems to be a joint military drill between China and Russia but it requires a further analysis," the Joint Chiefs of Staff said in a statement.

South Korea's military said the Chinese military told Seoul that its planes were conducting routine training before the Chinese aircraft entered the KADIZ. South Korea's military said the aircraft entered the zone around 8 a.m. local time and left around 3:20 p.m.

None of the aircraft violated South Korean territorial airspace, the military said.

Russia's Defense Ministry said two Russian Tu-95MS strategic bombers and four Chinese H-6K strategic bombers "carried out aerial patrols over the waters of the Japanese and East China Seas."

"The aircraft of both countries acted strictly in accordance with the provisions of international law. Violations of the airspace of foreign states were not allowed," the Russian Defense Ministry said, adding that the exercise was "not directed against third countries."

Russian Su-35S fighter aircraft escorted the bombers, along with A-50U airborne early warning and control aircraft, according to the ministry, which said that the bombers were accompanied by Japanese F-15 fighter jets "at certain stages of the route."

Japan's Defense Ministry released photos of the Russian and Chinese bombers and a map of their flight route, showing them flying through the Ryukyu Islands and through the Korea Strait between Japan and South Korea.

South Korea's Defense Ministry called both Russia and Japan and "expressed concerns" about the incident, according to Yonhap news agency, which also reported that South Korea's Foreign Ministry "called for measures to prevent a recurrence."

According to Russian news agency Interfax, Russia's military said this was the second joint long-range aviation patrol with China in the Asia-Pacific region.

The first such patrol took place in late July 2019 and prompted a strong response from Japan and South Korea, as the Russian planes involved reportedly flew into airspace around a group of islets that both Seoul and Tokyo claim, calling them Dokdo and Takeshima, respectively.

South Korean aircraft fired hundreds of warning shots toward the Russian military aircraft, and both South Korea and Japan accused Russia and China of violating their airspace, which Russia and China both denied.

The latest patrol reflects the warming relationship between Russia and China, who have grown closer amid worsening tensions with the US and its allies in the region.

The joint exercise was meant to "develop and deepen the comprehensive Russia-China partnership, further increase the level of cooperation between the two militaries, expand their ability for joint action and strengthen strategic stability," Russia's Defense Ministry said in a statement.

"The Russians and the Chinese have now entered the stage which I describe as near defense alliance. They're very, very close as two militaries," Alexey Muraviev, a professor at Australia's Curtin University and expert on the Russian military, told Insider in an interview this summer.

Muraviev said the July 2019 exercise was an example of the Chinese military learning from the Russian military.

"It wasn't just two pairs of strategic bombers," Muraviev said. "It was also a joint operation involving AWACS aircraft on both sides, so you have surveillance and intelligence systems talking to one another."

South Korea and Japan's territorial dispute is one of many disagreements the two US allies have, but it has long been "a latent difficulty" in their relationship, according to Sheila Smith, senior fellow for Japan studies at the Council on Foreign Relations.

That dispute has taken on new resonance as Moscow and Beijing grow closer, Smith told Insider in a recent interview.

"You've got a real sore spot that the Russians and Chinese ... took the moment to demonstrate the vulnerability" of, Smith said of the 2019 exercise. "Prior it was a political bone of contention, but now there's this other element to it where the Russians and the Chinese clearly feel they can exploit the differences between the US allies."

Reuters contributed to this report.