Media reports say South Korea has accused North Korea of blowing up an inter-Korean liaison office building north of the tense Korean border.

Seoul’s Unification Ministry said the destruction of the building in the North Korean border town of Kaesong happened at 2.49pm on Tuesday (June 17).

North Korea had reportedly earlier threatened to demolish the building as it stepped up its fiery rhetoric over Seoul’s failure to stop activists from flying propaganda leaflets across the border.

Some experts say North Korea is expressing its frustration because Seoul is unable to resume joint economic projects because of US-led sanctions.  ‘

The BBC says the move comes just hours after the North renewed threats of military action at the Korean border.

The site was opened in 2018 to help the Koreas - officially in a state of war - to communicate. It had been empty since January due to COVID-19 restrictions.

In a statement, South Korea reportedly warned it would “respond strongly” if the North “continues to worsen the situation.”

The destruction of the office, it said, “abandons the hopes of everyone who wanted the development of inter-Korean relations and peace settlement in the Korean Peninsula.”

“The government makes it clear that all responsibility of this situation lies in the North.”

The North Korean leader's sister, Kim Yo-jong - considered a close and powerful ally - threatened at the weekend to demolish the office, according to the BBC. 

Her brother, Kim Jong-un, has ruled North Korea as Supreme Leader since 2011.

There were hopes for improved relations between the North and the South and its close ally the US after U.S. President Donald Trump met Mr. Kim at the North-South border last June, but nothing materialized and the atmosphere has since deteriorated.