The South Korean military says North Korea fired what appear to be four shots from multiple rocket launcher systems on Sunday morning.

Military officials say the shots were fired from a location near South Pyongan Province toward the Yellow Sea, west of the Korean Peninsula, over the course of one hour from around 7:20 a.m.

They also say the artillery pieces flew about 30 kilometers and reached a maximum altitude of about 20 kilometers.

The South Korean government convened its National Security Council and stressed that it will keep monitoring North Korea's movements in the wake of a series of ballistic missile and other launches.

It also pledged to ensure that no security vacuum exists during the transition period to a new administration that is to be inaugurated in May.