Voting began for South Korea's presidential election early Wednesday, with the outcome of the race between ruling Saenuri Party candidate Park Geun-hye and main opposition rival Moon Jae-in expected to be decided by the slimmest of margins.

Before the blackout on all nationwide polls last week, Park, the 60-year-old daughter of late former President Park Chung-hee, was slightly ahead of Moon with her lead within the margin of error in most surveys taken.

Because of the slim lead, the Democratic United Party (DUP) claimed over the weekend that its hopeful effectively caught up with Park and could pull off an upset victory, while Saenuri countered that its contender has maintained her lead.

The country is expected to get the first glimpse of the winner at 6 p.m. when three major broadcasters will announce the results of joint exit polls right after ballot booths close.

In South Korea, presidential election day is a national holiday.

A clearer view of the election's outcome should be known within a few hours of the ballot counting process with the winner likely to emerge after 10 p.m. at the earliest, even if the final tally won't be completed until early Thursday.

The National Election Commission (NEC) said that voter turnout will probably be higher than the 63 percent reached in the 2007 race, when the one candidate had a clear lead over weaker rivals. A turnout of over 70 percent could occur as both the conservatives and liberals are expected to turn out en masse to vote for their candidates.

An earlier poll announced by the state election watchdog showed close to 80 percent of the 40.4 million eligible voters said they would cast ballots this year. The total number of voters eligible to cast there ballots rose by 2.81 million from the 2007 presidential election.

This year's race, meanwhile, showed all contenders calling for national unity, economic democracy, welfare and sweeping political and social reforms.

Park claimed if she is elected the nation's first woman president, every effort will be made to improve the livelihoods of the people and build up the middle class that had been hard hit by weak economic conditions.

Moon, a former human rights lawyer, has said that only by bringing about a change in government can meaningful political, economic and social reforms take place.

The NEC, meanwhile, said that besides the Sasenuri and DUP candidates there are four minor candidates running in the election, with one having quit on Sunday. Lee Jung-hee of the left-leaning Unified Progressive Party (UPP) dropped out of the race so as to give Moon a better chance at the polls.

In addition, before presidential candidates formally registered with the NEC on Nov. 25-26, one time independent hopeful Ahn Cheol-soo quit and declared his support for Moon.

Election experts added that this year will mark the third time automatic ballot-sorting machine will be used in the presidential election to speed up the counting process. (Yonhap News)