Seoul: South Korea's military said Thursday it scrambled fighter jets as two Chinese and four Russian military planes entered its air defence zone, an area wider than the country's airspace.
The Chinese and Russian planes entered and exited the Korea Air Defence Identification Zone (KADIZ) in the East Sea, also known as the Sea of Japan, from 11:53 am (0253 GMT) to 12:10 pm, Seoul's Joint Chiefs of Staff said.
But "there was no invasion of airspace", it added, and the South Korean military identified the planes "before they entered KADIZ, and deployed air force fighter jets to take tactical measures in preparation for contingencies".
An air defence identification zone is a broader area than a country's airspace in which it tries to control aircraft for security reasons, but the concept is not defined in any international treaty.
China's foreign ministry spokeswoman Mao Ning described the incident on Thursday as "a routine flight activity".
"As far as I know, I think this was a routine flight activity by Chinese military aircraft above international waters, which is understandable and in accordance with international law," she told a regular press briefing.
China and Russia are North Korea's traditional allies, and Washington warned last month that military ties between Pyongyang and Moscow were "growing and dangerous".
The United States has called on Beijing -- the North's biggest economic benefactor -- to restrain Pyongyang.
