According to reports, South Korea's military fired warning shots to drive away a North Korean warship that crossed the two nations' contentious maritime border.
The Northern Limit Line (NLL) was violated by a North Korean patrol boat at around 11 am on Saturday (2:00 GMT), according to the South Korean Joint Chiefs of Staff (JCS), which claimed to have fired warning shots and broadcast instructions to turn back.
"Our military maintains a decisive battle posture while monitoring the enemy's movements in preparation for potential provocations regarding NLL violations by North Korean patrol boats," the JCS stated.
Due to poor visibility, a South Korean patrol ship made "minor contact" with a Chinese fishing boat nearby during the operations. There were no safety issues, but the South Korean crew did sustain minor injuries, according to the JCS.
The alleged North Korean infiltration occurred when tensions rose over Pyongyang's stepped-up military actions recently, including Friday's test of a new solid-fuel intercontinental ballistic missile that experts say would enable missile launches without much advance notice.
Pyongyang has contested the NLL, created after the 1950–1953 Korean War, since the 1990s, claiming it should be much farther to the south.
The two Koreas exchanged warning shots in the western oceans in October, accusing one another of crossing the maritime border in a region where clashes have frequently taken place.
Since March, South Korea and the United States have been conducting their annual springtime drills. Pyongyang has threatened military retaliation, calling them a practice for nuclear war.
This week, North Korea's leader Kim Jong Un issued an order to intensify war deterrence in a "more practical and offensive" way to fight what the isolated nation referred to as US and South Korean aggression.
Seoul and Washington claim that the purpose of military drills is defensive and to dissuade Pyongyang.
Additionally, according to South Korean officials, North Korea has not responded to calls from South Korea on a series of cross-border inter-Korean hotlines for more than a week. This raises concerns about potential kinetic provocations as communications on those channels are intended to prevent unintentional clashes along the rival countries' sea borders.