North Korea on Tuesday blew up an inter-Korean liaison office in a border town, hours after the country renewed threats of military action against the South, BBC reported. The site, which is in the North’s territory, was opened in 2018 to help the leaders of the nations to communicate with one another in person, and has been empty since January because of the coronavirus-related restrictions.

South Korean border guards heard an explosion and then saw smoke rising from Kaesong, where the building was located, The New York Times reported.

Later, Seoul’s Unification Ministry confirmed the attack and said the destruction of the building at border town happened at 2.49 pm Tuesday, according to AP.

Kim Yo-jong, the sister of North Korean leader Kim Jong-un, had called the office rubbish that “must be thrown into the dustbin” and said that she would leave it to the military to come up with the next step of retaliation. Yo-jong had warned that “before long, a tragic scene of the useless North-South joint liaison office completely collapsed would be seen”.

“North Korea is frustrated that the South has failed to offer an alternative plan to revive the US-North talks, let alone create a right atmosphere for the revival,” Cheong Seong-chang, a director of the Sejong Institute’s Center for North Korean Studies told AFP. “It has concluded the South has failed as a mediator in the process.”

The inter-Korean liaison office was established to reduce tensions between the two Koreas.

Earlier in the day, the North Korean Army warned that it will re-enter border areas demilitarised under a peace pact with South Korea, if defector groups there continue to send propaganda leaflets across the border. The so-called demilitarised zone is a buffer along the border between North and South Korea that has separated the two countries since the Korean War in the 1950s.

Leaflets critical of North Korean leader Kim Jong-un and the regime’s disregard for human rights have become a source of tension between the two Koreas recently. Last week, Pyongyang cut all communications with the South, including a hotline between the two nations’ leaders, after it was angered by the pamphlets sent by defector groups. The sending of leaflets across the border was also banned under the 2018 inter-Korean agreement.