(ATTN: ADDS more details throughout, photos)
SEOUL, Dec. 22 (Yonhap) -- Nineteen Chinese and Russian aircraft entered South Korea's air defense identification zone (KADIZ) on Tuesday, prompting the Air Force to scramble fighter jets in response, the Joint Chiefs of Staff (JCS) said.
Four Chinese jets, believed to be H-6 bombers, first entered KADIZ above the East Sea, at around 8 a.m., according to the military.
A total of 15 Russian aircraft, including Tu-95 bombers, A-50 early warning aircraft, then flew in from the north, and they all left the zone at around 3:20 p.m., it added.
"Our military dispatched the Air Force fighter jets before their KADIZ entry in preparations for accidental situations," JCS said in a statement.
China and Russia appeared to have conducted a combined training, and none of the aircraft violated South Korea's territorial airspace, it added.
Before the aircraft's KADIZ entry, the Chinese military told South Korea its planes were carrying out normal training, according to officials.
South Korea and Russia do not have a military hotline. The two sides have been pushing to set up one between their air forces to exchange flight information, they said.
"We called military attaches of the two nations and expressed concerns about the incident," a defense ministry official said.
Foreign aircraft have often entered KADIZ. The last such incident took place in August when two Russian warplanes entered the zone above the southern sea and stayed there for around 30 minutes before moving into Japan's air defense identification zone.
Air defense identification zones are not territorial airspace and are not bound by international law. But a foreign warplane is supposed to make prior notification before approaching them in line with international customs to prevent accidental clashes.
Sino-U.S. tensions, tighter China-N.K. ties feared to weaken denuke efforts
Defense cost-sharing deal signals tighter, more stable S. Korea-U.S. alliance
Legislation on compensating virus-hit small biz picks up steam
Anger mounts over deepfake porn targeting Korean female celebs; more than 330,000 sign petition
Biden's pick for Asia policy likely to seek stronger regional alliances to check China