South Korea and Japan scrambled fighter jets on Thursday after Chinese and Russian aircraft were spotted near their countries, officials said.

South Korea scrambled fighters after two Chinese and four Russian military planes entered its air defense zone, South Korea's Joint Chiefs of Staff said in a statement.

Separately, Japan scrambled jets to monitor Chinese and Russian bombers and fighters conducting joint flights on Thursday, according to its defense ministry.

The aircraft included China’s H-6, J-16, Y-8 and Russia’s Tu-95, Su-35. They were spotted flying toward East China Sea through the channel between Japan and South Korea, Japan’s ministry said.

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According to South Korea's military, the aircraft entered the Korea Air Defense Identification Zone off its east coast between 11:53 a.m. and 12:10 p.m. local time and then left the area.

The planes did not violate South Korea's territorial airspace, which is protected by international laws, its military said. A defense zone is different from a nation's territorial airspace, which usually means the space above its territory, extending 12 nautical miles away from its coastline.

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There are no international laws that govern air defense zones, which are an area where countries themselves can uniquely and unilaterally require foreign aircraft to take steps to identify themselves, the International Civil Aviation Organization said, according to Reuters.

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Moscow does not recognize Korea's air defense zone, and Beijing similarly disputes that the zone is not territorial airspace.

The alleged violations came as Russian President Vladimir Putin was holding a news conference in his country, where he faces public questions concerning Moscow's war in Ukraine.

Reuters contributed to this report.