SEOUL, South Korea (AP) — South Korea’s military said it fired warning shots early Friday to drive away a North Korean merchant ship that briefly crossed the disputed western sea boundary between the rival neighbors.

The ship crossed the Northern Limit Line near the South Korean border island of Baengnyeong around 5 a.m. but retreated after South Korea's military issued an audio warning and fired warning shots, South Korea’s Joint Chiefs of Staff said.

There were no immediate reports that North Korean forces returned fire or responded with force.

The response was carried out in accordance with operational procedures and the military remains in a heightened state of readiness to firmly safeguard territorial waters, the South’s Joint Chiefs of Staff said.

South Korea’s military frequently has fired warning shots to repel North Korean patrol or commercial vessels breaching its waters. The poorly marked western sea boundary between the Koreas has been the scene of past skirmishes and attacks, including the North’s 2010 shelling of a South Korean island and its alleged torpedoing of a South Korean navy ship, which together killed 50 South Koreans.

During a fiery speech in January 2024, North Korean leader Kim Jong Un said his country does not recognize the Northern Limit Line in the Yellow Sea, which was drawn by the U.S.-led U.N. Command at the end of the 1950-53 Korean War. North Korea insists on a boundary encroaching deeply into South Korea-controlled waters.

The Koreas exchanged warning shots in 2022 after the South’s navy fired at a North Korean merchant ship that crossed the western sea boundary.

Tensions on the Korean Peninsula remain high as North Korea continues to dismiss Seoul’s calls to resume diplomacy. Relations have soured in recent years as Kim accelerated his weapons program and deepened alignment with Moscow following Russia’s invasion of Ukraine in February 2022.