By JOOHEE CHO, ABC News(SEOUL, South Korea) — North Korea has blown up the inter-Korean liaison office in their city of Gaesong, just above the North-South border, and the destruction was forewarned as part of Pyongyang’s series of threats to escalate tensions.The North has been sharply criticizing the South Korean government for not doing enough to stop citizens’ groups flying balloons into the North that contain anti-Pyongyang leaflets. “[The] South Korean government did show strong willingness to restrict these leaflets sent by North Korean defectors in the South. But North Korea is adamant to bring inter-Korean relations back to the hostile era and seems to conclude that there’s nothing more to expect from South Korean President Moon Jae-in,” Cheong Seong Chang, director of Center for North Korean Studies at The Sejong Institute in Seoul, told ABC News.The destruction is largely a symbolic act but designed to send a strong message to South Korea. Copyright © 2020, ABC Audio. All rights reserved.