Several Chinese and Russian military airplanes entered South Korea’s air defense zone on Tuesday.

According to the South Korean Joint Chiefs of Staff(JCS) on Tuesday, two Chinese military planes entered the Korean Air Defense Identification Zone(KADIZ) from 126 kilometers northwest of Ieodo reef off the southern coast at 7:56 a.m., flying toward the East Sea and exiting the zone at 9:33 a.m.

The Chinese planes, H-6 bombers, made another incursion into the KADIZ near Dokdo along with four Russian military aircraft, including Tu-95 bombers, with the duration of the second violation lasting around 17 minutes through 10:15 a.m.

None of the planes violated South Korea’s territorial airspace.

The JCS said that even before the aircraft entered the KADIZ, the South Korean military performed its usual tactical measures to respond to a possible accidental situation, such as scrambling of its fighter jets including F-15Ks and KF-16s.

The military presumed China and Russia were conducting a joint exercise, adding that further analysis is underway.

Tuesday marked the final day of U.S. President Joe Biden’s five-day trip to South Korea and Japan.