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

President Yoon Suk Yeol was detained, Wednesday, for questioning over his botched imposition of martial law, becoming the first sitting Korean president to be taken into custody.

The investigators are required to decide within 48 hours whether to file a formal arrest warrant to continue questioning him under custody or release him.

Investigators from the Corruption Investigation Office for High-ranking Officials (CIO) and the police arrived at the presidential residence compound in Hannam-dong, central Seoul, at around 4:30 a.m. More than 3,000 police officers were mobilized to execute the warrant to detain him and maintain public order around the area.

Following a standoff with Presidential Security Service (PSS) personnel that lasted about two and a half hours, investigators managed to move forward by passing through three layers of makeshift barricades set up the PSS, consisting of rows of guards and buses. To get past, the investigators had to climb over the buses using ladders.

The investigators then reached the nearest guard post to the residence. Several of them were allowed to pass, with presidential chief of staff Chung Jin-suk and Yoon's lawyer Yoon Kap-keun, granting permission for them to proceed.

At 10:33 a.m., the CIO said they executed the warrant. The detention came 43 days after Yoon declared martial law.

Graphics by Cho Sang-won

A convoy of vehicles, including one carrying the embattled leader, left the presidential residence and headed to the CIO headquarters in Gwacheon, Gyeonggi Province.

The CIO said it began questioning Yoon at around 11 a.m., with Lee Jae-seung, the deputy CIO chief, being the main investigator. Yoon's lawyers were also present, according to the agency.

Yoon refused to make a statement during the first questioning session that lasted through 1:30 p.m., the agency said. The CIO also did not record the questioning, because the president refused. According to the law, a suspect has the right to refuse such measures. Senior prosecutor Lee Dae-hwan of the CIO resumed the investigation in the afternoon.

After the questioning, Yoon is expected to be held at the Seoul Detention Center in Uiwang, Gyeonggi Province.

Yoon faces charges of leading an insurrection and abusing his power in connection with his martial law decree, which was lifted by the National Assembly just hours after its implementation.

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

Before heading to the CIO, Yoon released a pre-recorded address explaining that he had decided to appear for questioning to prevent a violent clash between investigators and the 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 legal authority to investigate the case, but simply a desire to prevent clashes,” Yoon said.

Hours after being taken into custody, the embattled president shared a handwritten letter on social media, justifying his martial law declaration as an exercise of presidential authority.

"Martial law imposition is not a crime. It was an exercise of presidential authority to save the country from a national crisis," Yoon wrote.

Chung said, "We said Yoon will voluntarily appear before the CIO, but the CIO insisted on executing the warrant. In response, the president said, 'The most important thing is that people don't get hurt,' and decided to comply with the detention warrant. He also said he will fight until the end."

The presidential office convened an emergency meeting later in the day to discuss possible countermeasures in response to Yoon's detention.

“Yoon said he will not be discouraged by the wrongful detention. In his impeachment trial [at the Constitutional Court], Yoon will reveal the unfairness of the impeachment motion and the emergency political crisis the country is currently facing,” Yoon's lawyer Seok Dong-hyun told reporters.

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

It was the second attempt by investiators to detain the president. The first attempt on Jan. 3 failed after a nearly six-hour standoff with the PSS. Yoon had vowed to “fight to the end” after defying the law enforcement officials' first attempt.

The joint investigation team, consisting of the CIO, the police and the defense ministry's investigation unit, had 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.

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

Large crowds gathered outside the residence, with police estimating that around 6,500 supporters of the president were present. Some of Yoon's die-hard supporters staged protests by lying on the ground to protest the CIO's execution of the warrant. Around 30 lawmakers from the ruling People Power Party (PPP) were also among the crowd.

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

A warrant was also issued to detain the PSS' acting chief, Kim Sung-hoon, who led Yoon's security service in blocking access to the presidential residence. Kim failed to respond to a third summons requested by the police. Park Chong-jun, the former PSS chief, resigned on Friday before appearing for police questioning.

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