North Korean boats strayed into South Korean waters across the de facto border on Tuesday but turned back after warning shots from a South Korean Navy ship.
Around 4 p.m. that day, one North Korean ship and two patrol boats crossed the Northern Limit Line southwest of Yeonpyeong Island, the Joint Chiefs of Staff here said.
The South Korean Navy immediately dispatched a high-speed boat to the scene, where it sent a warning message and fired about 10 warning shots, according to the JCS.
A military spokesman said the North Korean boats turned back across the NLL around 5 p.m.
At the time, about 50 Chinese fishing boats were catching fish in nearby waters, and no special North Korean military movements were detected, the spokesman added.