The South Korean military is on heightened alert as signs have been detected which show the North may fire a short-range missile into the Yellow Sea.

A military source says Pyongyang’s ban of ships from waters near Jeungsan County in South Pyeongan Province from Monday through Wednesday indicates a possible missile launch in the near future.

The source speculates the North might fire its short-range surface-to-air KN-O1 missile, which has a maximum range of 160 kilometers.

Following the detonation of a nuclear device in North Hamgyeong Province on Monday, North Korea launched a short-range missile from its base in Musudan-ri around noon, and two more missiles from Wonsan, Gangwon Province, around five p.m.