This comes after North Korea blew up a joint liaison office. The destruction in the city of Kaesong came hours after North Korean Supreme Leader Kim Jong-un threatened to advance the military in previously withdrawn border areas. A spokesman from the Blue House in Seoul said: “The government expresses strong regret over North Korea’s unilateral detonation of the inter-Korean liaison office building.
“We sternly warn that we will strongly respond to it if North Korea takes any action that further worsens the situation.
“The government makes it clear that all responsibility of this situation lies in the North.”
The office was the first South Korean presence north of the border since the end of the Korean War.
According to the Times, it had been closed since January as a coronavirus precaution.
Kim Yo-jong, the sister of Kim, said in a Sunday statement: “We will soon take a next action.
“Before long, a tragic scene of the useless North-South joint liaison office completely collapsed would be seen.”
In a report, Pyongyang backed Korea Central News Agency said: “At 14:50, the liaison office was tragically ruined with a terrific explosion.
It added the action would “surely force human scum and those who have sheltered the scum, to pay dearly for their crimes”.
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Seoul had paid $8.6million (£6.9million) to reopen the office after a cooling of tensions between the two Koreas.
Pyongyang also closed a hotline between the two leaders.
Donald Trump also called for a “all or nothing” agreement in which Pyongyang gives up its nuclear arsenal, as well as biological and chemical weapons.
Kim has called for the parties to build up trust for lesser agreements.
Pyongyang offered to close down a nuclear plant at Yongbyon in return for an easing of some international sanctions.
Trump turned down this offer.
The North Korean’s military previously said it was now ready to “turn the front line into a fortress and heighten military vigilance”.
South Korea’s defence ministry said it was monitoring the situation with the US.
Mrs Kim ended her Sunday statement with: “Rubbish must be thrown into the dustbin.”