A record number of South Koreans participated in early voting for the presidential election set to be held next week, poll officials said on Friday.

As of 1 pm, about 7.72 million people, or 18.17 per cent of the electorate, cast their ballots since the two-day advance voting began on Thursday, the National Election Commission (NEC) said.

This is already higher than the overall early voting rates of 12.2 per cent for the parliamentary elections in 2016 and 11.5 per cent for the local elections in 2014, Yonhap News Agency reported.

Turnout in the nation's first early voting for a presidential election was the highest in South Jeolla province, a liberal stronghold, with 25.21 per cent, and the lowest in the traditionally conservative city of Daegu with 15.42 per cent, the NEC said.

Early voting is being conducted at 3,507 polling stations across the country. It will end at 6 p.m.

Over 42.4 million people are eligible to cast ballots in the upcoming election, marking the largest number of voters in the country's history.

All votes cast in advance will be kept sealed with those locked overseas to be brought here for official counting following the end of the presidential election on May 9, the election watchdog added.

Currently, 13 hopefuls are vying for the presidential office after two candidates dropped out of the race.

The latest poll published on Wednesday showed Moon Jae-in of the liberal Democratic Party in the lead with 42.4 percent, followed by two runner-ups — Ahn Cheol-soo of the centre-left People's Party and Hong Joon-pyo of the former ruling Liberty Korea Party — who were tied at 18.6 per cent.