North Korean fishing boats on Saturday again crossed over the Northern Limit Line in the West Sea, the de facto maritime border between the two Koreas. It was the second incursion across the NLL in two days.

South Korean naval boats fired warning shots on Friday to repel fishing vessels that had crossed into South Korean waters. "A North Korean fishing boat crossed around 400 m south of the NLL on Saturday morning northwest of Yeonpyeong Island," a military spokesman here said Sunday. "The vessel moved back north immediately after we gave it a warning."

North Korean fishing boats also crossed the NLL on Sept. 12, 14, 15 and 20, venturing anywhere between 0.7 km to 2.2 km south. Last Friday, six boats crossed, prompting South Korean gunboats to fire warning shots to force them to retreat.

North Korea apparently readied coastal artillery each time its fishing boats crossed the NLL. North Korean state TV over the weekend called the South Korean warning shots "military provocations" and accused Seoul of treating North Korean fishing boats like Chinese trawlers illegally fishing there as an excuse to attack them.

North Korea does not recognize the NLL, which it says was unilaterally drawn by U.S.-led forces at the end of the 1950-53 Korean War. It wants a new border drawn farther south.