The sister of North Korean leader Kim Jong Un said it is "high time" to break relations with South Korean authorities, adding the next action against the "enemy" will come from the army.

It's better to take a series of retaliatory measures rather than release statements condemning South Korea's behavior, and which could be misinterpreted or dismissed, Kim Yo Jong said via the official Korean Central News Agency on Saturday.

"Rubbish must be thrown into dustbin," she said. "By exercising my power authorized by the Supreme Leader, our party and the state, I gave an instruction to the arms of the department in charge of the affairs with enemy to decisively carry out the next action."

Kim Yo Jong's comments came on the 20th anniversary of the first meeting between top leaders of the divided Koreas. The summit beginning on June 13, 2000, was the biggest moment of then-President Kim Dae-jung's reconciliation effort that led to stepped-up trade and joint projects and helped earn the South Korean leader the Nobel Peace Prize.