Japan and South Korea scrambled fighter jets to protect their skies after Russia and China conducted joint patrols in the region, intensifying fears of a fresh global conflict. Chinese and Russian bombers and fighter jets flew over the western Pacific Ocean and East China Sea as part of a 10th joint strategic air patrol exercise on Tuesday, according to China’s defence ministry.

The aircraft entered South Korea‘s air defence zone for an hour, according to the country’s official Yonhap news agency, prompting its defence ministry to lodge a diplomatic protest with representatives of China and Russia over the “potential violation”.

Japan’s defence ministry also described the exercise as a matter of “serious concern for our national security”. Both countries deployed their own jets to monitor the patrols and “take tactical measures in preparation for any contingencies”, according to reports.

Lee Kwang-suk, director general of the International Policy Bureau at Seoul’s defence ministry, said: “Our military will continue to respond actively to the activities of neighbouring countries’ aircraft within the KADIZ (Air Defence Identification Zone) in compliance with international law.”

Japanese minister of defence, Shinjiro Koizumi, also confirmed that military aircraft had been deployed to “strictly implement” air defence measures following the reported China-Russia patrol.

He said on social media that two Russian “nuclear-capable Tu-95 bombers” flew from the Sea of Japan to the Tsushima Strait before meeting with two Chinese jets “capable of carrying long-range missiles”.

Mr Koizumi added that the patrol was then joined by at least eight other Chinese J-16 fighter jets and Russian A-50 aircraft on a flight “around” Japan.

“The repeated joint flights of bombers by both countries signify an expansion and intensification of activities around our country, while clearly intending to demonstrate force against our nation, posing a serious concern for our national security,” he wrote.

The renewed tension follows a growing distance between China and Japan, with the latter’s Prime Minister warning Xi Jinping that Tokyo could respond to Chinese military action in Taiwan if it posed a threat to national security last month.

Beijing said the joint drills with Russia were carried out according to “annual cooperation plans”, with Moscow also confirming that the exercise had lasted eight hours and that aircraft had been at one stage “followed by fighter jets from foreign states”.

While China and Russia have regularly flown military jets near South Korean and Japanese airspace in “joint exercises” in recent years, the deepening of a divide between the two autocracies, both allies of North Korea, and the democratic world, means incursion into air defence zones could pose a greater threat than ever.