An unanswered phone call at the inter-Korean liaison office put Seoul officials on edge for hours Monday, as it came after North Korea’s threats to shut it down completely.

The Unification Ministry said that the North finally answered its phone call in the afternoon, after missing earlier ones in the morning.

The two Koreas exchanged communication at the scheduled 5 p.m., but the North did not mention why it skipped the earlier call, according to the ministry.

There were speculations that the reclusive regime is acting true to its warning of abolishing the office, when it didn’t respond to Seoul’s call in the morning -- for the first time since the office’s opening in 2018.

The two Koreas have made calls through the inter-Korean liaison office every day at 9 a.m. and 5 p.m. since the office was opened in the border town of Kaesong in September 2018, after the historic Panmunjeom summit between North Korean leader Kim Jong-un and President Moon Jae-in. The office, established to reduce tension between the two sides, has been temporarily closed since late January due to the coronavirus outbreak, but the calls and communication continued.

Last Thursday, Kim Yo-jong, the leader’s influential younger sister, warned of a number of consequences if Seoul failed to prevent defector-run civic groups from sending balloons carrying propaganda leaflets over the Demilitarized Zone. They included shuttering the liaison office, permanently closing the long-suspended industrial park in Kaesong and scrapping the 2018 cross-border military agreement.

The North has long taken issue with the balloon launches, calling them “acts of war,” and warned Seoul to halt the activities. The balloons typically carry pamphlets condemning the reclusive regime, human rights abuses and Kim’s leadership, while promoting democracy and capitalism -- as well as USB memory sticks and $1 bills to encourage North Koreans to pick them up.

Just a few hours after Kim Yo-jong issued the threats, the Unification Ministry revealed its plans to introduce a law banning the balloon launches. Despite Seoul’s promise to do so, the North’s United Front Department, which is in charge of inter-Korean affairs, released a statement the next day vowing to put Kim Yo-jong’s words into action.

The North has been ratcheting up its threats since then, with the state’s mouthpiece Rodong Sinmun condemning the balloon launches as worse than military provocations and as a “serious threat” to its leadership and system.

Meanwhile, Kim Jong-un presided over a politburo meeting of the ruling Workers’ Party on Sunday and discussed measures to develop the chemical industry, but inter-Korean issues and ongoing tensions were not mentioned, according to the Korea Central News Agency on Monday.

During the session, he stressed the importance of chemical industry as the “foundation” and “a major thrust front of the national economy.”

Kim Yo-jong, whose official title is first vice department director of the party’s Central Committee, also attended the meeting.

The meeting also discussed the need for the country to achieve economic self-sufficiency and improve living conditions in Pyongyang, as well as changes to the party’s rules and party organization matters.

Meanwhile, the military communication lines between the two Koreas were operating normally on Monday, according to the Defense Ministry.

By Ahn Sung-mi (sahn@heraldcorp.com)