Friday’s incursion by North Korean fishing boats may have been an intentional provocation, warned Seoul’s Unification Minister Monday. Speaking to foreign journalists at a press event on September 24, Minister Yoo Woo-ik also said given the frequent incursions by North Korean fishing vessels across the Northern Limit Line, it was difficult for South Korea’s government to believe such territorial trespasses were accidental.

The Northern Limit Line is a de facto maritime border between the Koreas drawn up shortly after the Korean War by the U.N. Command. It’s been the scene of frequent military clashes between North and South Korea; the North has never recognized the NLL and resents this boundary in the West Sea off the Korean Peninsula, which interferes with its access to rich crabbing grounds south of the line.