South Korea's left-wing presidential frontrunner Lee Jae-myung on Friday proposed amending the constitution to make it more difficult to impose martial law, aiming to prevent political crises like the one that erupted last year.

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.

South Korea presidential candidate Lee Jae-myung proposed amending the constitution to tighten restrictions on the declaration of martial law.