The flight by two Russian Tu-95 strategic bombers and two Chinese H-6 bombers, backed up by a Russian A-50 early warning plane and its Chinese counterpart, a KJ-2000, marks a notable ramping-up of military cooperation between Beijing and Moscow.
Russia has said it carried out its first long-range joint air patrol with China in the Asia-Pacific region, a mission that triggered hundreds of warning shots from South Korean jets and a strong protest from Japan.
The operation will concern leaders from Washington to Tokyo and could complicate relations and raise tension in a region that has for years been overshadowed by hostility between the United States and North Korea.
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While troops and naval ships from Russia and China have taken part in joint war games before, they have not, according to Russia’s ministry of defence, conducted such air patrols in the Asia-Pacific region together until Tuesday.
“The joint patrol was carried out with the aim of deepening Russian-Chinese relations within our all-encompassing partnership, of further increasing cooperation between our armed forces, and of perfecting their capabilities to carry out joint actions, and of strengthening global strategic security,” the ministry said in a statement.
Seoul and Tokyo, who both scrambled jets to intercept the planes, accused Russia and China of violating their airspaces, an allegation Moscow and Beijing denied.
South Korean warplanes fired hundreds of warning shots towards the Russian A-50 military aircraft, defence officials in Seoul said, saying it was the first time a Russian military aircraft had violated South Korean airspace. Moscow denied all of those assertions.
In Washington, the Pentagon said it supported South Korea and Japan’s responses.
Dmitri Trenin, director of the Carnegie Moscow Center and a former colonel in the Russian army, predicted Russian-Chinese joint air patrols would soon be common in the region.
“Such patrols will become a regular feature under a new agreement soon to be signed between Moscow and Beijing,” Trenin said on Twitter. “Russo-Chinese entente grows thicker.”
Lt-Gen Sergei Kobylash, commander of Russia’s long-range aviation, said in televised comments that the Russian planes had been airborne for 11 hours and covered around 9,000 km (5592 miles).
Foreign fighter jets had escorted them on 11 separate occasions, he added.
The South Korean defence ministry said the Russian and Chinese bombers had entered its air defence zone together early on Tuesday.
The separate Russian A-50 airborne early warning and control aircraft later twice violated South Korean airspace over Dokdo – an island that is controlled by Seoul and claimed by both South Korea and Japan.
Russia’s defence ministry said it did not recognise South Korea’s defence zone, while the Chinese foreign ministry said the area was not territorial airspace and that all countries enjoyed freedom of movement in it.
South Korean fighters did not fire any warning shots toward Russia’s two bombers, the Russian defence ministry said in a statement, which made no mention of any A-50 aircraft.
It accused the two South Korean F-16 fighter planes of carrying out “unprofessional manoeuvres,” of crossing the path of the Russian bombers, and of not communicating with them.
If the Russian pilots had felt any threat to their safety, their response would have been swift, it added.
Separately, Japan, which said it had also scrambled fighter aircraft to intercept the Russian and Chinese planes, lodged a complaint with both South Korea and Russia over the incident.