South Korea's conservative presidential candidate Kim Moon-soo came to prominence as a maverick right-wing politician but it was only the latest metamorphosis in a life that saw him espouse liberal causes as a labour activist when he was younger.

After months of political turmoil, South Koreans will head to the polls Tuesday to elect a president to succeed disgraced former leader Yoon Suk Yeol, who was ousted from office over his ill-fated decision to impose martial law in December.

Voters headed to polling stations across South Korea on Thursday morning as early voting began for the country’s snap presidential election, said local media reports.