South Korea's military said it scrambled fighter jets as two Chinese and six Russian warplanes entered its air defense zone on Wednesday.
The two Chinese H-6 bombers repeatedly entered and left the Korea Air Defense Identification Zone (KADIZ) off South Korea's southern and northeast coasts starting at around 5:50 a.m. (2050 GMT Tuesday), Reuters quoted Seoul's Joint Chiefs of Staff (JCS) as saying.
They re-entered the zone hours later from the Sea of Japan, known in South Korea as the East Sea, together with the Russian warplanes, including TU-95 bombers and SU-35 fighter jets, and left after 18 minutes in the KADIZ, the JCS said.
"Our military dispatched air force fighter jets ahead of the Chinese and Russian aircraft's entry of the KADIZ to implement tactical measures in preparation for a potential contingency," the JCS said in a statement.
The planes did not violate South Korea's airspace, it said.
An air defense zone is an area where countries demand that foreign aircraft take special steps to identify themselves.
Unlike a country's airspace - the air above its territory and territorial waters - there are no international rules governing air defense zones.
Moscow does not recognize Korea's air defence zone. Beijing said the zone is not territorial airspace and all countries should enjoy freedom of movement there.
Japan's Air Self Defense Force also scrambled fighter jets after the Chinese bombers flew from the East China Sea into the Sea of Japan, where they were joined by two Russian drones, Tokyo's defense ministry later said in a press release.
China and Russia have previously said their warplanes were conducting regular joint exercises.
