The South Korean military says North Korea fired four more short-range ballistic missiles toward the Yellow Sea shortly before noon on Saturday.

South Korea's Joint Chiefs of Staff said the North fired the missiles from around 11:32 a.m. to 11:59 a.m.

They said the missiles flew at a top speed of Mach 5, or five times as fast as the speed of sound, traveling about 130 kilometers at an altitude of some 20 kilometers.

Pyongyang has expressed strong opposition to the latest large-scale joint air drills by US and South Korean forces, which continued for six days through Saturday. US and South Korean militaries are on alert for further missile launches by the North.