South Korea's liberal party candidate Lee Jae-myung is projected to win Tuesday's snap presidential election by wide margins, according to exit polls, ushering in a political sea change after backlash against martial law brought down his predecessor.

Results of the surveys by the country's broadcasters were released after nearly 80 percent of the country's 44.39 million eligible voters had cast their ballots.

South Koreans are hoping to put six months of turmoil from ousted leader Yoon Suk-yeol's martial law decree behind them and for a reversal in the ebbing fortunes of Asia's fourth-largest economy.

The joint exit poll by broadcasters KBS, MBC and SBS, which has in previous elections mostly been in line with the final results, put Lee of the Democratic Party on 51.7 percent and his conservative rival Kim Moon-soo on 39.3 percent.

A separate survey by broadcaster JTBC put Lee on 50.6 percent and Kim on 39.4 percent. Channel A also predicted a Lee win by similar margins.

After being impeached by parliament in December, Yoon was removed from office by the Constitutional Court on April 4, less than three years into his five-year term, triggering the snap election that now stands to remake the country's political leadership and foreign policies.

Lee had called the election "judgement day" against the previous Yoon administration and the conservative People Power Party, accusing them of having condoned the martial law attempt by not fighting harder to thwart it and even trying to save Yoon's presidency.

"I hope the issues surrounding martial law are addressed more clearly and transparently," said 40-year-old Seoul resident Kim Yong-Hyun. "There are still many things that don't make sense, and I'd like to see them properly resolved."

Park Chan-dae, acting leader of the Democratic Party, told KBS that the party was holding out for the votes to be officially counted, but that the projections suggest voters rejected the martial law attempt and are hoping for an improvement in their livelihoods.

"I think people made a fiery judgement against the insurrection regime," he said.

The winner must tackle challenges including a society deeply scarred by divisions made more obvious since the attempt at military rule, and an export-heavy economy reeling from unpredictable protectionist moves by the United States, a major trading partner and a security ally.

If the exit polls' projections are accurate, Lee should be on course to officially become president when the National Election Commission declares the winner sometime on Wednesday, immediately taking power including becoming commander-in-chief of the military. (Reuters)