SEOUL – South Korea scrambled fighter jets after two warplanes from China and four from Russia briefly entered an air identification zone maintained by Seoul, raising tensions on the highly militarised peninsula.

The Russian and Chinese aircraft were in South Korea’s Air Defence Identification Zone from between 11.53am and 12.10pm on Dec 14, Yonhap News agency reported, citing the Joint Chiefs of Staff (JCS).

The six planes departed the area and did not enter South Korean airspace, the JCS said.

The air zone is not South Korea’s territorial airspace, but is an area where aircraft are supposed to identify themselves as they draw near it.

The planes flew above waters between South Korea and Japan, the JCS reportedly said, and were in the general vicinity of an island claimed by Seoul and Tokyo.

When asked about the incident on Dec 14, China Foreign Ministry spokeswoman Mao Ning said at a regular press briefing in Beijing that it was “a routine activity” and “it’s in line with international law”.

In June, four warplanes each from Russia and China entered the area known as Kadiz, prompting South Korea to rush its jets into the air.

The flights come as the two Koreas have backed away from a 2018 deal to reduce tensions along their border.

After North Korea fired a rocket into space in November that deployed a spy satellite, South Korea restarted surveillance flights it had halted, and North Korea threatened action against the aircraft from its neighbour.

Russia has been looking to enlist North Korea in joint military exercises that include China.

During a rare trip to Pyongyang in July, Russian Defence Minister Sergei Shoigu proposed to leader Kim Jong Un that they hold joint naval drills that included China, Yonhap reported, citing South Korea’s spy agency.

There is no indication that North Korea accepted the offer.

Mr Kim’s state media on Dec 14 slammed the US, Japan and South Korea for their plan to launch a system this month to share real-time data on missile launches from North Korea, saying the move is pushing the region toward conflict. BLOOMBERG