TOKYO — Japanese F-15 fighter jets on Saturday conducted an air exercise with U.S. B1-B bombers in the skies above the East China Sea, Japan’s Air Self Defense Force (ASDF) said.

The joint drill comes as South Korea braces for a possible further missile test by North Korea as it marked its founding anniversary, just days after its sixth and largest nuclear test rattled global financial markets and further escalated tensions in the region.

The exercise involved two U.S. Air Force B-1B Lancer bombers flying from Andersen Air Force Base on the U.S. Pacific island territory of Guam, which were joined by two Japanese F-15 jet fighters.

On Aug. 31, Japanese F-15 fighter jets also conducted an air exercise with U.S. B1-B bombers and F-35 stealth fighters in skies south of the Korean peninsula, two days after North Korea launched a ballistic missile over northern Japan.