China and Russia conducted a joint military air patrol over the Sea of Japan and the East China Sea on Tuesday, prompting South Korea to deploy fighter jets to guard against any emergency.
This is the sixth such patrol carried out by Beijing and Moscow in the region since 2019.
The official Xinhua news agency, citing China's Defense Ministry, reported that the two militaries conducted their sixth joint air patrol, in accordance with the annual plan for military cooperation between China and Russia.
The ministry gave no details about the nature, route and location of the agencies involved in the patrol over these vast maritime expanses between the Korean peninsula, Japan, China and Taiwan.
South Korea's military confirmed it immediately deployed fighter jets after four Russian and four Chinese military aircraft entered its air defense identification zone in the south and east of the Korean Peninsula.
"We have deployed Air Force fighters to take tactical action in preparation for an emergency," the Joint Chiefs of Staff said.
Russian and Chinese aircraft have not violated South Korean airspace.
An air defence identification zone is a large area unilaterally defined by States in which foreign aircraft are required to identify themselves for reasons of national security.
The Chinese and Russian breach of South Korea's air defense identification zone came after South Korean, U.S. and Japanese defense ministers affirmed their commitment to strengthening trilateral security cooperation on the sidelines of the Shangri-La Dialogue, an annual security conference held in Singapore over the weekend.