And amid rising tensions on the Korean peninsula, North Korea has deployed surface-to-air missile systems to its west coast near the West Sea border with the South.
According to an anonymous government source, the Russian manufactured surface-to-air guided missiles, SA-2, have been deployed in the area since Tuesday's bombardment of Yeonpyeong Island.
The source said SA-2 missiles seem to be targeting South Korea's fighter jets flying near the disputed western maritime border, known as the Northern Limit Line.
In addition surface-to-water-missiles including Samlet and Silkworm, which are capable of destroying targets at ranges of up to 96 kilometers, have been put in place as South Korea and the US kicked-off a four-day joint naval drill on Sunday.