SEOUL, South Korea >> North Korea threatened to permanently shut a liaison office with South Korea as it continued to condemn its rival for failing to prevent activists from sending anti-North Korean leaflets across the border.

The statement by North Korea’s ruling Workers’ Party today came a day after the powerful sister of leader Kim Jong Un said her country would end a military agreement reached with South Korea in 2018 to reduce tensions if Seoul fails to stop the activists.

Kim Yo Jong also said North Korea could permanently shut the liaison office and a joint factory park in the border town of Kaesong, which have been symbols of reconciliation between the two countries.

Desperate to keep alive a faltering diplomacy with North Korea, South Korea in response said it would push new laws to ban activists from flying leaflets by balloon to the North, which triggered a debate over freedom of speech.

But an unidentified spokesman of the Workers’ Party’s inter-Korean Affairs Department said Seoul’s promise lacked sincerity, and the scrapping of the liaison office will be the first in a series of North Korean steps that would cause extreme suffering for the South.

The statement also confirmed an elevated status for Kim Yo Jong, who was described as her brother’s top official for inter-Korean affairs.

Under her instructions, North Korea has decided as a first step to “definitely withdraw the idling (North-South) joint liaison office housed in the Kaesong industrial zone,” the statement said.

“We do not hide that we have had long in mind decisive measures to fundamentally remove all provocations from the South and to completely shut down and remove all the contact leverage with the (South),” said the spokesman of the party’s United Front Department.

Referring to the leaflets, the spokesman said the “nonstop disposal of dirty rubbish from the South side has exhausted us so much as to come to a clearer conclusion that enemies are enemies after all.”

“Our determination is to follow as far as the evil cycle of the confrontation leads while facing the situation squarely, because our path is always straight.”

South Korea’s government had no reaction to the statement Saturday morning. In a speech marking South Korea’s Memorial Day, President Moon Jae-in vowed to strengthen the nation’s defense, but he made no mention of North Korean threats to abandon inter-Korean peace agreements.

Sending balloons across the border has been a common activist tactic for years, but North Korea considers it an attack on its government. Defectors and other activists in recent weeks have used balloons to fly leaflets criticizing Kim Jong Un over his nuclear ambitions and dismal human rights record.

While Seoul has sometimes sent police officers to block such activities during sensitive times, it had previously resisted North Korea’s calls to fully ban them, saying the activists were exercising their freedom.

The liaison office in Kaesong has been closed since late January after the Koreas agreed to temporarily shut it until the coronavirus is controlled.

It is also the location of a now-shuttered factory complex that was jointly run by the two Koreas. It combined South Korean capital and technology with cheap North Korean labor. Seoul’s previous conservative government shut it down in 2016 following a North Korean nuclear test, removing a crucial cash source for North Korea’s struggling economy.

During their summits in 2018, Kim and Moon agreed to the military pact aimed at reducing conventional threats and vowed to resume operations at the Kaesong factory park and South Korean tours to a resort at North Korea’s Diamond Mountain when possible, expressing optimism that U.S.-led sanctions on the North would end.

But North Korea has suspended virtually all cooperation with South Korea in recent months amid a stalemate in larger nuclear negotiations with the Trump administration, which have faltered over disagreements on sanctions relief in exchange for disarmament steps.

North Korea has sped up its missile tests while also pressuring Seoul to break away from Washington and restart joint economic projects held back by the sanctions over its nuclear program.