South Korea's impeached President Yoon Suk Yeol has spent his first night incarcerated as a pre-trial inmate at the Seoul Detention Centre after a court issued a formal detention warrant on Sunday to hold him for up to 20 days.

South Korea's impeached president, Yoon Suk Yeol, was formally arrested early Sunday, days after being apprehended at his presidential compound in Seoul, as he faces possible imprisonment over his ill-fated declaration of martial law last month.

Yoon, who was impeached and suspended from office in December, is the first sitting South Korean president to be arrested.