Vehicles leave the presidential residence in Seoul, Wednesday, to head for the Corruption Investigation Office for High-ranking Officials headquarters in Gwacheon, Gyeonggi Province. President Yoon Suk Yeol was in one of them. He was detained for questioning over his botched martial law. Korea Times photo by Shim Hyun-chul

Investigators detained President Yoon Suk Yeol at 10:33 a.m. Wednesday to question him over his short-lived martial law last month.

Yoon is the first sitting Korean president to be detained. The detention comes 43 days after he declared martial law on Dec. 3, which lasted only six hours.

A convoy of vehicles believed to be carrying Yoon left the presidential residence in Hannam-dong, central Seoul, and headed to the Corruption Investigation Office for High-ranking Officials (CIO) headquarters in Gwancheon, Gyeonggi Province.

The CIO began interrogation at 11 a.m.

President Yoon Suk Yeol enters the the Corruption Investigation Office for High-ranking Officials headquarters in Gwacheon, Gyeonggi Province, Wednesday, to be questioned over his martial law imposition. Korea Times photo by Choi Won-suk

Before heading to the CIO, Yoon released a pre-recorded address in which he said he decided to appear before the CIO to prevent a violent clash between investigators and the Presidential Security Service (PSS) personnel.

However, he maintained that the investigation and the warrant were illegal.

"As the president who must defend the Constitution and legal system, responding to this illegal and invalid warrant execution is not an acknowledgment of the CIO's authority to investigate the case, but simply a desire to prevent clashes," Yoon said.

President Yoon Suk Yeol delivers an address at the presidential residence in Seoul, Wednesday, before being detained to be questioned over his martial law fiasco. Courtesy of presidential office

The outcome came hours after investigators entered the presidential residence compound earlier in the morning in their operation to execute the warrant.

It was the investigative authorities' second such attempt, with the first attempt on Jan. 3 failing after a nearly six-hour standoff with the PSS.

They arrived in front of the presidential residence compound in Hannam-dong, central Seoul, at 4:20 a.m. with some 3,000 police officers.

Although confronting PSS personnel for about two and a half hours, investigators managed to move forward by passing through three layers of makeshift barricades which the PSS made with rows of guards and buses. The investigators had to climb over the buses with ladders.

Investigators walk toward the presidential residence in Hannam-dong, Seoul, after passing through a barricade of buses, Wednesday. Yonhap

As of 8:15 a.m., they arrived at the nearest guard post to the residence. Several of them entered past the post, with presidential chief of staff Chung Jin-suk and Yoon's lawyer Yoon Kap-keun allowing them to proceed.

The joint investigation team, consisting of the CIO, the police and the defense ministry's investigation unit, have vowed to implement more forceful measures this time.

"There was no physical clash during the execution of the warrant. PSS personnel didn't block us when entering the presidential compound," the CIO said. Acting President Choi Sang-mok issued a statement urging the CIO and the PSS to ensure there are no physical clashes.

Large crowds gathered outside the residence, with police estimating that around 6,500 supporters of Yoon were present.

Around 30 lawmakers from the ruling People Power Party (PPP) were also among the crowd.

"The CIO has aroused public concern and confusion with their illegal warrant execution," Rep. Kim Gi-hyeon of the PPP said.

Police officers march toward the presidential residence compound in Seoul, Wednesday, to detain President Yoon Suk Yeol. Korea Times photo by Shim Hyun-chul