South Korea’s Marine Corps conducted an artillery drill near the inter-Korean border in the Yellow Sea to mark the sixth anniversary of North Korea’s deadly shelling of Yeonpyeong Island in the Yellow Sea.

The Northwestern Islands Defense Commands said that the sixth Marine Brigade conducted the exercise at a unit on the island on Tuesday.

The exercise involved K-9 self-propelled howitzers and AH-1S Cobra attack helicopters, firing about 18-hundred shells.

An official at the Marine Corps said that in the live-fire drill, the Marines exercised shooting at the North’s frontline units on Jangjae, Gal and Mahap islets, which North Korean leader Kim Jong-un visited recently. 

The commands said that it issued a warning on vessels traveling in the area ahead of the routine artillery drill, which was held in the presence of officials from the Military Armistice Commission.