South Korea scrambles fighter jets as Russian and Chinese planes enter defense zone

South Korea deployed fighter jets on Tuesday after Russian and Chinese planes entered its defense zone unexpectedly.

An air defense identification zone is an area where countries ask that foreign aircraft identify themelves before entering.

Four Russian and two Chinese jets failed to do that as they crossed the defense zone over the Sea of Japan for about 17 minutes, according to South Korea's Joints Chiefs of Staff.

The planes did not enter South Korea's actual airspace above its territory.

China has taken a harder line against South Korea in recent years, appearing to punish the country for moving closer to the US on economic and diplomatic issues.

READ MORE: US-South Korean drills send threatening message to China and North Korea

There are no international laws that govern air defense zones.

Russia doesn't recognize South Korea's, and China has claimed that any country should be free to move there.

The US, South Korea and Japan held their first stand-alone trilateral summit in August.

Days later, the US and South Korea held routine joint military drills.

The drills are meant to send "an unequivocal messages to North Korea and China that the US knows how to accomplish its military goals - so don't try anything dumb," one former naval and intelligence officer told the Daily Express US.

Chinese media have been keen to crticize South Korea for its continued coziness with the West in recent years.

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