SEOUL (AFP) — South Korea’s military fired warning shots after a North Korean vessel entered its waters, prompting the ship to retreat, Seoul said Friday.

The North Korean merchant ship crossed the maritime boundary, known as the Northern Limit Line (NLL), northwest of Baengnyeong Island at around 5 a.m. on Friday, South Korea’s Joint Chiefs of Staff (JCS) said.

“Our forces issued warning broadcasts and fired warning shots, after which the vessel retreated beyond our waters,” the JCS said in a statement.

The military added that they responded in “accordance” with procedures while “closely monitoring North Korea’s movements.”

North Korea does not formally recognize the NLL.

The incident comes two days after South Korea conducted live firing drills at the NLL.

The two Koreas technically remain at war because the 1950-53 Korean War ended in an armistice, not a peace treaty.