President Yoon Suk Yeol declared martial law on December 3 and sent soldiers and helicopters to parliament but was forced to rescind the decree hours later after lawmakers voted it down.

Defence minister Kim Yong-hyun resigned last Thursday and was formally arrested Tuesday on charges including "engaging in critical duties during an insurrection" and "abuse of authority to obstruct the exercise of rights".

During a parliamentary hearing, the commissioner general of the Korea Correctional Service said the former minister tried to kill himself minutes before his arrest was announced.

Shortly before midnight (1500 GMT Tuesday), "former Minister of Defence Kim Yong-hyun attempted suicide at the Seoul Dongbu Detention Center," said Shin Yong-hae.

Adding that he received the report Wednesday morning, Shin said Kim had tried to kill himself in the toilet using a string from his clothing.

"A control room staff member intervened, and when they opened the door, he immediately gave up the attempt," said Shin.

Shin added that Kim was now under protection in a secure cell and in good health.

"The medical examination results indicate that the inmate's health status is good without any abnormalities, and he is currently living a normal life in the facility," the justice ministry said in a statement sent to AFP.

Kim had issued an apology on Tuesday, saying through his lawyers that "all responsibility for this situation lies solely with me".

He "deeply apologised" to the South Korean people and said that his subordinates were "merely following my orders and fulfilling their assigned duties".