North and South Korea exchanged hundreds of rounds of artillery fire on Friday near the Northern Limit Line, the maritime border between the two peninsular powers.

The demonstrations of artillery prowess began with North Korea lobbing over 200 artillery rounds into the sea, in what Pyongyang described as a “natural response” to provocations by the “military gangsters” of South Korea.

The South Korean military carefully monitored the North’s artillery exercise and determined that none of the shells passed over the Northern Limit Line. However, the South Korean military ordered civilians on nearby Yeonpyeong Island to move into shelters as a precaution.

Yeonpyeong Island was hit by North Korean artillery fire in November 2010, killing two South Korean marines and two civilians. Some of the family members of the dead feel the South Korean government downplayed North Korea’s murderous actions in the interest of avoiding a wider conflict. Pyongyang said it attacked the island because South Korea fired into its territorial waters during an artillery drill.

Yeonpyeong has about 2,000 civilian residents and troops, including an artillery unit. The South Korean Marine Corps quickly arranged its own artillery exercise, firing about 400 shells from Yeonpyeong and another base in the area, Baengnyeong Island.

South Korean Defense Minister Shin Won-sik and South Korea’s Joint Chiefs of Staff observed the reciprocal live-fire drill. Shin said North Korea’s artillery fire was an “act of provocation that escalates tension and threatens peace on the Korean peninsula.”

“Our military must assume the readiness to completely wipe out the enemy so that they wouldn’t dare another provocation, and to back up the pace through strength,” he said.

Tensions have been rising between the two Koreas since North Korea launched its first spy satellite in November. A 2018 military agreement between the two countries was abandoned soon afterward. Last week, North Korean dictator Kim Jong-un said peaceful reunification of the two Koreas was impossible and is no longer a goal of his regime.

Friday’s barrage of shells was North Korea’s first provocative artillery display since the 2018 military agreement was scrapped. 

The U.S. and South Korea wrapped up a week-long live-fire exercise north of Seoul on Thursday, involving armor, artillery, and aircraft. North Korea denounced the exercise, as it does with all joint U.S.-South Korean drills, and vowed to retaliate against the “mad dogs” who conducted it.