
Border incidents between the two Koreas are closely watched by both countries, which have officially been in a state of war since the 1950-53 Korean War ended with an armistice not a peace treaty.
The North Korean fishing boat crossed the border at around 9.30am (12.20am GMT) off the west coast of the peninsula and was then seized and towed to South Korea’s Baengnyeongdo island for investigation, Yonhap said, citing the Joint Chiefs of Staff.
The South Korean military fired a warning shot at a North Korean patrol boat that briefly crossed the border while tracking the fishing boat, it said.
South Korea’s defence ministry did not immediately respond to a request for comment.