ISTANBUL

South Korea’s impeached President Yoon Suk Yeol on Wednesday defended his short-lived attempt to impose martial law last month, amid reports that a man committed suicide by self-immolation soon after the 63-year-old leader was detained.

Yoon's defense of the emergency law came hours after police raided the presidential residence in the capital Seoul, where they detained Yoon, who had been avoiding arrest since Jan. 3.

“Martial law is not a crime. Martial law is an exercise of presidential authority to overcome a national crisis,” Yoon wrote in a handwritten letter posted on his Facebook account.

The 63-year-old leader remains in custody of the Corruption Investigation Office for High-Ranking Officials (CIO) at its office in Gwacheon, south of Seoul.

Soon after Yoon was taken into custody, a man set himself on fire near the parking lot of the CIO headquarters at around 8.05 p.m. (1105GMT) and was transferred to a hospital but he succumbed to his injuries, the JoongAng Daily reported.

Investigation is underway to establish the circumstances of the self-immolation while the deceased man’s identity remains unknown.

Investigators were successful in their second attempt to detain Yoon at 10.33 a.m. local time (0133GMT) on Wednesday after presidential security blocked an initial attempt on Jan. 3.

After he was taken to the anti-graft office in Gwacheon, the formal questioning began at 11 a.m. (0200GMT) in the presence of Yoon's lawyers.

Yoon, however, has refused to testify before the investigators.

The suspended president was provided with a lunch box after interrogation over his brief declaration of martial law on the night of Dec. 3.

Yoon is the first South Korean president to be detained and face charges of insurrection and treason.

Sitting presidents are immune to criminal investigation in South Korea but for the two cited reasons.

Yoon was impeached on Dec. 14 and is facing trial by the Constitutional Court, which has up to six months to decide whether to remove or reinstate him as president.