South Korea’s president defended his martial law decree as an act of governance and denied rebellion charges, vowing to 'fight to the end' in the face of attempts to impeach him and intensifying investigations.

South Korean President Yoon Suk Yeol said he would "fight to the end" on Thursday as his own political party shifted closer to voting with the opposition to impeach him over his short-lived martial law order.

South Korean President Yoon Suk Yeol on Thursday vowed to fight "until the very last minute", in a defiant address defending his shock decision to declare martial law and deploy troops to the country's parliament last week.