Security Ministry officials said in a statement they would take "substantial measures to physically remove" people spreading the slander, South Korea's Yonhap News Agency reported.
The statement cited a report by an Internet news service based in Seoul that claimed North Korean leader Kim Jong-un had presented senior members of the country's Communist party with copies of "Mein Kampf," Adolf Hitler's autobiography, to learn from Hitler's experiences before World War II.
The ministry charged the report had belittled Kim's "great personality."
A South Korean official responded that "threatening physical harm against defectors will not be tolerated" and that "resolute action" would be taken if Pyongyang carried out its threats.
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