South Korea sent a message of “strong complaint” to Russia over its military aircraft’s violation of Korean airspace, Cheong Wa Dae said Tuesday. Seoul has also filed formal complaints to China over its military aircrafts entering the Korea Air Defense Identification Zone.

Earlier in the day, a number of Chinese and Russian military aircrafts engaged in a joint drill entered the KADIZ, with one Russian plane twice entering Korean airspace over the Dokdo Islets in the East Sea.

The Chinese and Russian aircrafts had also entered the Japanese Air Defense Identification Zone, prompting Japan to scramble jets in response.

According to Cheong Wa Dae spokesperson Ko Min-jung, the National Security Office monitored the situation from early on, and National Security Director Chung Eui-yong sent a message to Nikolai Patrushev, the secretary of the Security Council of the Russian Federation.

“We consider the developments very gravely, and a much stronger measures will be taken if such actions are repeated. (Seoul) requests FSC to assess the situation and take appropriate steps,” Cheong Wa Dae spokesperson Ko Min-jung quoted Chung’s message to Patrushev.

Russia has refuted Seoul’s claims, saying its military aircrafts were engaged in planned drills over international waters.

“Two Tu-95 strategic bombers of Russia’s aerospace forces carried out a planned flight in the airspace above the neutral waters of the Sea of Japan,” Moscow’s Foreign Ministry said in a statement.

Moscow also denied that South Korean jets that were dispatched in response fired warning shots, saying there were no attempts to communicate with Russian pilots. Seoul’s Ministry of National Defense had announced earlier that Russian aircrafts did not respond to communications, and that South Korean fighter jets had fired the shots.

Moscow also said that South Korean jets had taken “unprofessional maneuvers” that threatened the safety of the Russian jets.

China, meanwhile, claimed that the KADIZ is not Korean airspace, and that other countries have freedom to navigate in the area under international law.

According to Japanese news reports, Tokyo has lodged complaints to Seoul and Moscow over the incident, claiming sovereignty over the Dokdo Islets.

Japanese reports citing an unnamed government source claimed that Tokyo filed a complaint saying that it “cannot accept such actions in our territory.”

Following the incident, Seoul’s Ministry of Foreign Affairs and Ministry of National Defense summoned diplomats and military attaches of the two countries stationed in Korea to lodge complaints.

According to the Foreign Ministry, Deputy Minister for Political Affairs Yoon Soon-gu summoned Maxim Volkov, the deputy chief of the Russian Embassy in Seoul, and Chinese Ambassador Qiu Guohong to deliver formal complaints.

Seoul’s Defense Ministry delivered similar complaints to Chinese defense attache and Russian military attaches for navies and air forces.

“(A message was sent that) the government and the public consider Russian military aircraft violating airspace over Dokdo to be a grave issue, and that Russia was warned that the government would take appropriate steps, with all possibilities open, if such actions are repeated in the future,” the Defense Ministry said in a statement.

By Choi He-suk (cheesuk@heraldcorp.com)