The North promised a "merciless military strike" because sending the leaflets would be "an unpardonable challenge to the army and people" of North Korea, Yonhap News Agency reported.
A group of North Korean defectors plan to launch balloons carrying the leaflets on Monday from Imjin Pavilion just south of the border.
Sending the leaflets amounts to "undisguised psychological warfare," said the statement from the North's Korean Central News Agency (KCNA), quoting the Western Front Command of the North Korean army.
KCNA warned inhabitants of Imjin Pavilion to evacuate the area "in anticipation of possible damage."
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