US and South Korean jets take part in an air exercise. (Photo: South Korean Ministry of National Defense)

For the five-day exercise, the allies mobilized some 100 air assets each, including F-15K and KF-16 jets from South Korea and F-16s from the US, the source said, noting no military assets were deployed from the US mainland this time.

The allies have regularly held the air exercise in a scaled-down, subdued manner since they suspended the large-scale Vigilant Ace exercise which supported peace efforts on the Korean Peninsula.

North Korea has long denounced the allies' military drills as a war rehearsal for an invasion and used them as an excuse for provocations.