The South Korean military said Thursday it deployed fighter jets when two Chinese military aircraft and four Russian military planes entered its air defense zone.
The Chinese and Russian aircraft entered and exited the Korea Air Defense Identification Zone (Kadiz) in the East Sea, also known as the Sea of Japan, between 11:53 a.m. (2:53 p.m. GMT) and 12:10 p.m., Joint Chiefs of Staff said.
But there was “no invasion of airspace,” the General Staff emphasized, the South Korean army identified them “before they entered Kadiz and used air force fighter aircraft to take tactical measures and prepare for all eventualities.”
An air defense identification zone is an area larger than a country's airspace in which the country attempts to control aircraft for security reasons. However, this concept is not defined in any international treaty.
China and Russia are North Korea's traditional allies and Washington warned last month that military ties between Pyongyang and Moscow were particularly “growing and dangerous.”
The United States has called on Beijing, the North's biggest economic booster, to rein in Pyongyang.
Thursday's incident came a week after U.S. national security adviser Jake Sullivan said Washington and its Asian allies Seoul and Tokyo would “defend” peace and stability in the Taiwan Strait.
The three allies also reiterated their commitment to “freedom of navigation” in the disputed South China Sea area.
China views Taiwan as a province that has not yet succeeded in reunification with the rest of its territory since the end of the civil war in 1949.
In recent years, Beijing has increased military pressure on the island and promised to one day take it.
Taiwan is a key point of tension between China and the United States, Taipei's main ally.
Last month, the commissioning of Malligyong-1, North Korea's first spy satellite, led to the South partially abrogating a five-year-old military agreement and the North completely abrogating it in a bid to ease bilateral tensions.
According to Seoul, Pyongyang received aid from Moscow in exchange for the supply of weapons used in Russia's war against Ukraine.
Back in June, South Korea deployed fighter jets as Chinese and Russian warplanes conducted joint air maneuvers near its airspace over the Sea of Japan and the East China Sea.
As with Thursday's incident, none of them had violated South Korean airspace at the time.