North Korea on Tuesday blew up a building where its officials and their South Korean counterparts had recently worked side by side, dramatically signalling its displeasure with the South after weeks of threats to end the countries’ recent détente.

South Korean border guards heard an explosion and then saw smoke rising from Kaesong, the North Korean town where the building was located. The building appeared to be blown completely apart in a blast so powerful that windows in nearby buildings were also shattered, according to video footage from a South Korean surveillance camera on the border.

The South’s unification ministry confirmed that North Korea had demolished the four-storey glass-and-steel building that housed what had been known as the joint liaison office. Hours later, the North’s official news agency said “the liaison office was tragically ruined with a terrific explosion”, adding that the action reflected “the mind-set of the enraged people” of North Korea.

The office, staffed by personnel from both sides, was opened in 2018, at a time when the North Korean leader, Kim Jong-un, and President Moon Jae-in of South Korea had held optimistic meetings.