China's defense ministry says the air forces of China and Russia conducted their sixth joint aerial strategic patrol over the Sea of Japan and the East China Sea on Tuesday.

The ministry said in a statement that the patrol was carried out in accordance with the China-Russia annual military cooperation schedule. It did not reveal the types of aircraft or the specific airspace in which they flew.

Last November, the defense ministries of the two countries said their strategic bombers held joint patrols over the Sea of Japan and the East China Sea.

In March, Chinese President Xi Jinping and Russian President Vladimir Putin agreed to conduct joint patrols and military drills on a regular basis.
They also agreed that the two countries would boost military exchanges and cooperation.

The South Korean military's Joint Chiefs of Staff said four Chinese and four Russian military planes flew over the Sea of Japan and entered South Korea's air defense identification zone south of the Korean Peninsula for about 2 hours from around noon Tuesday. It added that they did not violate South Korea's airspace.

The military said it identified the planes before they entered the defense identification zone, and that it had deployed fighter jets in preparation for potential accidental situations.

South Korea's Yonhap News Agency said the planes may have included bombers. The agency also said South Korea issued warnings about the flights, and that China responded on a hotline that they were a regular exercise.