Kim Jong Un draws red line at sea, renews promise to fire on South Korean ship 'that violates even 0.001mm'

North Korea's supreme leader has drawn a red line at sea, vowing to fire upon any South Korean vessel that even barely crosses it.

Kim Jong Un reportedly attended the test launch of a new surface-to-air missile on Wednesday, where he told military officials to be prepared for a strike against any South Korean ship that enters North Korea waters from now on.

The supreme leader "stressed the need for the DPRK to thoroughly defend the maritime sovereignty by force of arms and actions, not by any rhetoric, statement and public notice," according to state-owned and operated news outlet Korean Central News Agency.

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DPRK is an abbreviation of Democratic People's Republic of Korea — the official name of the North Korean nation.

"He gave important instructions to bolster up military preparedness particularly in the border waters north of Yonphyong Island and Paekryong Island frequently invaded by the enemies' warships including destroyers, escort ships and speedboats," KCNA reported.

The Northern Limit Line (NLL) is the internationally accepted maritime line dividing North Korea and South Korea at sea — this standard border has been challenged by Kim Jong Un's regime in the past.

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Because of Kim Jong Un's frequent arguments that North Korean waters extend slightly farther to the south of the NLL, the exact parameters of the red line in the supreme leader's threats are somewhat hard to understand — making the situation even more volatile.

"What is clear is that when the enemy intrudes into the maritime border recognized by us, we will regard it as an encroachment upon