Rep. Ahn Gyu-back, second from right, and opposition lawmakers head to the prison wing of Seoul Dongbu Detention Center in Seoul, Wednesday. Yonhap

The National Assembly's planned on-site questioning session at Seoul Dongbu Detention Center, aimed at directly questioning key figures involved in the Dec. 3 martial law declaration, was canceled after former Minister of National Defense Kim Yong-hyun refused to cooperate.

Earlier in the day, lawmakers from the Assembly's special committee investigating insurrection charges against the Yoon Suk Yeol administration visited the facility. As lawmakers from the ruling People Power Party (PPP) boycotted the visit, only opposition lawmakers were present.

A witness seat with a nameplate reading "witness Kim Yong-hyun" had been prepared in the detention center's main conference room. Despite the setup, Kim declined to appear, insisting he could not attend the session due to "trial preparation." The former defense chief, who was deeply involved in planning and implementing the martial law, also refused to attend previous parliamentary hearings held by the special committee.

A nameplate reading "witness Kim Yong-hyun" is placed on a desk at the main conference room of Seoul Dongbu Detention Center in Seoul, Wednesday. Yonhap

"As committee chair, I cannot help but express deep regret over the witness's disrespectful attitude, which disregards public opinion and the authority of the National Assembly," said Rep. Ahn Gyu-back, a member of the main opposition Democratic Party of Korea (DPK) chairing of the special committee on the insurrection investigation. He added that the committee would file a complaint against Kim for contempt of the Assembly at next week's plenary session.

"Refusing to cooperate with the investigation is an outright rejection of the truth. If he is so confident and honorable, why can't he stand in front of the public?" DPK Rep. Han Byung-do added.

DPK Rep. Park Sun-won also denounced the PPP lawmakers of the committee for boycotting the sessions.

"Their refusal to participate in the most crucial witness investigation is essentially an act of endorsing and condoning the insurrection — signaling that they will continue to do so in the future," Park said.

An empty witness desk with the nameplate of ex-Defense Minister Kim Yong-hyun is placed on a desk at the main conference room of Seoul Dongbu Detention Center in Seoul, Wednesday. Yonhap

In the afternoon, the special committee lawmakers visited Seoul Detention Center in Uiwang, Gyeonggi Province, where President Yoon Suk Yeol and former Defense Intelligence Command leader Noh Sang-won are imprisoned, to hold another questioning session. But the session was also scrapped when Yoon declined to cooperate.