South Korea's military said on Friday it scrambled fighter jets after two Chinese and seven Russian warplanes intruded into its air defense identification zone during what Beijing called regular training.

The Chinese and Russian aircraft entered the northeastern part of the Korea Air Defense Identification Zone (KADIZ) for a unspecified period of time before exiting, Seoul's Joint Chiefs of Staff (JCS) said, adding that they did not violate its airspace.

The JCS dispatched fighter jets and air refueling tankers as an unusual step to brace for a potential contingency.

The Chinese military said in response to a query that its planes were carrying out routine drills, the JCS said.

"We assess the situation as joint Chinese and Russian military exercises but additional analysis is needed," the JCS said in a statement.

Chinese and Russian warplanes have often entered the zone in recent years amid conflicting claims over various Air Defense Identification Zones (ADIZ).

Unlike airspace, an ADIZ is usually an area where countries may unilaterally demand that foreign aircraft take special steps to identify themselves, with no international laws governing ADIZs.

Moscow does not recognize KADIZ, while Beijing said the area is not territorial airspace and all countries should enjoy freedom of movement there.

In 2019, South Korean warplanes fired hundreds of warning shots toward Russian military aircraft when they entered South Korean airspace during a joint air patrol with China.

South Korea and Japan had scrambled jets to intercept the patrol at the time, accusing Russia and China of violating their airspace, which Moscow and Beijing denied.