The figure will later be combined with turnout during last week's two-day early voting period, which came to 26.04 percent.

The turnout marked the highest rate ever in early voting, apparently indicating high public interest in the election that followed the first impeachment of a president.

The election comes in the wake of the March 10 ouster of former President Park Geun-hye over a massive corruption scandal that also led to her arrest and indictment.

Thirteen candidates are vying for the top elected office, but many believe the election is, in reality, a three-way race between Moon Jae-in of the liberal Democratic Party, Hong Joon-pyo of the conservative Liberty Korea Party and Ahn Cheol-soo of the center-left People's Party.

Moon, together with his wife, cast his ballot at a polling station in northwestern Seoul.

"I felt the people's earnest desire for government change to create a country worthy of being called a country," he told reporters at the station set up at a middle school. "I plead with you to join forces to build a country worthy of being called a country by participating in the vote until the end."

Hong Joon-pyo, the nominee of the conservative Liberty Korea Party affiliated with Park, cast his ballot at a polling station in southern Seoul, also with his wife, saying he will wait for the people's judgment.

"This election is a war of regime choice in which people will accept the pro-North Korea, leftist administration or choose a government that will defend the free Republic of Korea," he said, apparently referring to Moon's campaign.

Speaking to reporters after casting his ballot in northeastern Seoul, Ahn Cheol-soo, the presidential candidate of the center-left People's Party, said he expects the nation to make a wise choice.

"It was a very short election period, but I did my best to explain my vision, policy and values," he said. 

Yoo Seong-min of the conservative Bareun Party, which splintered off from Park's party after her impeachment, returned to his hometown of Daegu, 302 kilometers southeast of Seoul, to vote.

"I think this election is a very important election that should properly transform the world," he said to his supporters there.

"Please don't obsess over a mere change of government, but think carefully about who is the person to truly change the world, and if you pick me, I am confident I will fulfill my duties well."

Rep. Sim Sang-jeung, the candidate of the progressive Justice Party, cast her vote at a polling station in her electoral district in Goyang, northwest of Seoul.

"I trust that (the people) will vote for Sim Sang-jeung to achieve stronger reform and greater change," she said.

Voting was set to end at 8 p.m. instead of the usual 6 p.m. because it was a by-election.

"There was high participation in overseas voting and early voting conducted in advance, and a voter survey by the commission shows that more people are eager to vote," an NEC official told Yonhap by phone. "We expect turnout to reach the 80 percent level."

If the rate exceeds 80 percent, it would mark the first time since the presidential election in 1997 that participation has been so high.

Unlike the previous elections, the president-elect will be inaugurated immediately after an official declaration of his or her victory by the NEC in a meeting slated for early Wednesday.

The election had been considered tilted in favor of liberal candidates from the very onset as it followed the removal of the former conservative president over corruption allegations.

Hong, the candidate from the former ruling party, however, was seen catching up with his liberal rivals at the last minute.

The last opinion poll on the election published Wednesday had Hong and Ahn tied at 18.6 percent in second place, while Moon led the race with 42.4 percent. The publication of new opinion polls has been prohibited to prevent the outcome of an opinion poll itself affecting the outcome of an election.

A total of over 42.4 million people, or 82 percent of the country's 51 million population, were eligible to vote in the presidential election, marking the largest number of voters in the country's history. (Yonhap)