China’s Defence Ministry has acknowledged it carried out joint air patrols with Russia on Tuesday, but denied the planes had crossed into airspace controlled by South Korea, which fired warning shots in response. South Korea and Japan scrambled jets on Tuesday morning after Russian bombers and Chinese military planes were accused by Seoul of breaching its airspace, which is also claimed by Japan. South Korea’s Defence Ministry said this was the first incursion by Russian planes and that its jet had fired hundreds of warning shots to ward off two Chinese H-6 bombers and two Russian TU-95 bombers. The incident has threatened a diplomatic crisis, with officials in Seoul issuing harsh warnings to the head of Russia’s Security Council, Nikolia Patrushev, and summoning Russian and Chinese diplomatic staff to urge them to prevent a repeat of Tuesday’s incident. Japan, which also claims the airspace the Russian and Chinese jets flew through, said South Korea had no right to respond to the violation. Russia's Defence Ministry on Tuesday also denied the patrol had entered Seoul’s airspace and instead accused the Korean jets of “dangerous” manoeuvers and failing to communicate with the Russian pilots. Later, it said that "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." Yoon Do-han, a press secretary at South Korea's presidential office, on Wednesday said that an unnamed Russian military attaché in Seoul blamed a technical malfunction for the incursion. "Russia has conveyed its deep regret over the incident and said its defence ministry would immediately launch an investigation and take all necessary steps," Mr Yoon said. "The officer said such a situation would have never occurred if it followed the initially planned route." Officials in Washington said they backed statements issued by Japan and South Korea, who are traditional allies of the United States. Russian and Chinese military cooperation has strengthened as political and economic ties between Moscow and Beijing have deepened. For the first time ever, Chinese ground troops participated in Russia's Vostok military exercises in 2018. Dmitry Trenin, the director of the Carnegie think tank’s office in Moscow, said this type of drill would become a more regular feature in the region and that the exercises were a sign of deepening ties between Moscow and Beijing. The incident “involving Russia and the Republic of Korea warplanes over Sea of Japan highlights the first ever joint Russian-Chinese air patrol,” he wrote on Twitter. “Such patrols will become a regular feature under a new agreement soon to be signed between Moscow and Beijing.” He added: “The Russo-Chinese entente grows thicker.”