Hours after North Korea demolished the inter-Korean liaison office in its border town of Kaesong in a surprise provocation Tuesday, South Korea warned of a strong response if the North further worsens the situation.

Cheong Wa Dae made the unusually strong warning after holding an emergency meeting of the National Security Council (NSC) standing committee to discuss the matter.

"The government expresses strong regret over North Korea's unilateral explosion of the inter-Korean liaison office building," Kim You-geun, deputy director of Cheong Wa Dae's national security office, told reporters after the meeting. "We sternly warn that we will strongly respond to it if North Korea takes any action that further worsens the situation."

Kim also said the demolition constitutes an action that betrays "the expectations of all people who wish for the development of inter-Korean relations and the settlement of peace on the Korean Peninsula."

"We make it clear that the responsibility for anything that could happen because of the act lies entirely with the North Korean side," he said.

The meeting came after the North blew up the communication office, established in 2018 as a symbol of inter-Korean reconciliation.

According to the defense and unification ministries, North Korea detonated the inter-Korean liaison office in its border town of Kaesong at 2:49 p.m. The North's Korean Central News Agency later confirmed that the country "completely ruined" the building.

The explosion took place three days after Kim Yo-jong, the powerful sister of North Korean leader Kim Jong-un, warned that the North will demolish the "useless" communication office in protest of Seoul's "failure" to stop activists from sending anti-North Korean leaflets into the country.

The North also last week threatened to cut off all communication lines with South Korea and has since been out of touch with the South.

The Tuesday NSC meeting in Seoul was presided over by Chung Eui-yong, director of the national security office at Cheong Wa Dae.

President Moon Jae-in was not present. Moon has not presided over a plenary NSC session since March last year, shortly after the North Korea-US summit meeting in Hanoi, Vietnam ended without results. 

Two previous NSC sessions this month also did not include Moon, including the last meeting held on Sunday. (Yonhap)