South Korea's impeached President Yoon Suk Yeol refused to be questioned by investigators on Monday under a probe into whether he committed insurrection, as dozens of his supporters faced being charged over a violent rampage on a court building.

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.