North Korea recently held a large-scale military exercise off its eastern coastal city of Wonsan last Friday, using missile bases in South Korea as virtual targets.
The North's Korean Central News Agency on Sunday unveiled a photo of leader Kim Jong-un observing the drill.
A Seoul official said that during the amphibious landing exercise Spike missile units on Baengnyeongdo and Yeonpyeongdo islands were included as targets.
South Korea's recently deployed Israel-made Spike missiles, with a range of around 20 kilometers, can launch precision strikes on the North’s hidden coastal artillery.
For the exercise on Friday, Pyongyang mobilized an 18-hundred-ton Romeo-class submarine, a fire support vessel with 122-milimeter multiple rocket launchers, hovercrafts, transport aircraft for special commandos and several cannons.