The North Korean military is known to have recently tested anti-ship missiles in the Yellow Sea.

A South Korean military source says that North Korea test-fired the missiles from its IL-28 bomber into Yellow Sea waters on two occasions last month and early this month.

The missiles are known to be a modified version of the North's Styx ground-to-ship missiles which are deployed on the coastline north of the Northern Limit Line on the Yellow Sea, which serves as the de facto inter-Korean maritime border.

The South Korean military believes that North Korean provocation by means of firing missiles on South Korean vessels is a possibility and authorities are bolstering defense counter measures.