Former South Korean President Yoon Suk Yeol is back in custody over an independent investigation into his declaration of martial law last year.

Former South Korean President Yoon Suk Yeol was back in a solitary jail cell on Thursday with basic food and a khaki prison uniform after prosecutors secured a new detention warrant over his bid to impose martial law last year.

Yoon, who was the first sitting South Korean president to be arrested, faces trial on charges of leading an insurrection over his attempt to impose martial law. During Wednesday's seven-hour hearing, a special counsel team argued for the arrest warrant on five key charges, South Korean news agency Yonhap reported.