South Korean Defense Ministry, on Wednesday, strongly protested Russian and Chinese intrusion of its air defense identification zone (KADIZ) without notice calling on the two countries to avoid repeating the incident.

On Tuesday, four Chinese and Russian military jets briefly breached South Korea's KADIZ without encroaching on its airspace. Nevertheless, according to South Korean media, Seoul dispatched its air force fighters to engage in tactical action to avert any potential accidents.

According to AFP, an ADIZ is an area wider than a country's airspace in which it tries to control aircraft for security reasons, but the concept is not defined in any international treaty.

According to the published statement, "The defense ministry expressed regret to both countries in connection with the fact that Chinese and Russian military planes entered our air defense identification zone (KADIZ) without any advance notice and flew over ... areas close to our air space."

Moreover, the Defense Ministry's statement urged "appropriate measures to be taken to prevent the repetition of such actions, as they could become a source of tension in the region."

Lee Seung-beom, the defense ministry's director general for internal policy, reportedly expressed "strong protest" to the Russian and Chinese military attaches in South Korea, the ministry reported.

China and Russia conducted joint air force patrols over the Sea of Japan and the East China Sea on Tuesday, as South Korea said it had deployed warplanes in response to fighter jets allegedly near its airspace.

In a statement, the Chinese Defense Ministry said Beijing and Moscow "staged the sixth joint aerial patrol in accordance with an annual military cooperation plan between China and Russia."

The statement gave no further details of the drills, which took place over waters bordering Japan, the Korean peninsula, and Taiwan.

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