Unification Minister Kim Yung-ho attends a Cabinet meeting at the government complex in Seoul, Dec. 3. Yonhap

Unification Minister Kim Yung-ho and the spy agency chief have undergone questioning by investigators as part of their ongoing probes into President Yoon Suk Yeol's short-lived imposition of martial law this month, officials said Sunday.

Kim underwent questioning by police for six hours Saturday over his attendance at a Cabinet meeting that took place shortly before Yoon's declaration of martial law on Dec. 3, making him the latest participant of the gathering to appear before investigators.

Police have now questioned ten of the 12 participants of the Cabinet meeting, including Prime Minister Han Duck-soo. Yoon and former Defense Minister Kim Yong-hyun have yet to undergo police questioning.

Separately, Cho Tae-yong, the head of the National Intelligence Service (NIS), was recently questioned by prosecutors in their own investigation, judicial sources said. Cho, who is not a Cabinet member, was among the 12 participants of the Dec. 3 meeting.

Prosecutors reportedly questioned Cho over whether he was informed of alleged orders from Yoon to arrest politicians during martial law.

Hong Jang-won, former first deputy director of NIS, has claimed he received such orders from Yoon but Cho deferred from immediately taking action when he reported them.

The NIS has rejected Hong's claims of making such a report to Cho as false.

Police have been separately investigating the martial law episode from the prosecutors through a joint investigation team with the Corruption Investigation Office for High-ranking Officials and the defense ministry's investigative unit.

On Sunday, the CIO also questioned Maj. Gen. Moon Sang-ho, head of the Defense Intelligence Command, over his alleged role in the martial law declaration, days after his arrest Friday.

The CIO has been pushing to step up its investigation, summoning Yoon to appear for questioning on Christmas Day, following his refusal to cooperate with a summons request last week. (Yonhap)