Seoul, Sep 22 (IANS): North Korea has deployed six more patrol vessels near the sea border with South Korea as Pyongyang continues its campaign to invalidate the maritime boundary in the Yellow Sea.

"The North Korean military has stationed six additional patrol ships near the Northern Limit Line and newly built artillery bunkers inside the island of Gal this year," the South Korean navy said in a statement on Tuesday.

According to the statement, through the additional deployment and intensified artillery power in the Yellow Sea border area, North Korea is continuing its schemes to nullify the NLL which marks the disputed western border between the two countries, Yonhap News Agency reported.

North Korea often sends ships across the maritime border and launches provocations, challenging the legitimacy of the NLL imposed by the US-led United Nations Command after the 1950-53 Korean War.

The statement also confirmed that North Korea has recently constructed more artillery bunkers on Gal island, located 4.5 km from the South Korean island of Yeonpyeong, which was bombarded by Pyongyang in 2010.