Park Geun-hye, the 60-year-old candidate of the conservative Saenuri party, was leading by a narrow margin in last week’s polls, the last one allowed under election rules, Reuters has reported. She stands a chance to become the first female president of South Korea.
Park faces stiff challenge from Moon Jae-in, the 59-year-old left-leaning candidate of the Democratic United Party and a former human rights lawyer who has promised greater engagement with North Korea.
The race pitted the two against each other after popular software tycoon Ahn Cheol-soo pulled out of the contest and declared his support for Moon.
The winner of Wednesday's race will assume office in February 2013, at a time when Seoul is facing numerous challenges, including strained ties with Pyongyang, a slowing economy, aging population, and rising welfare expenditure.
Polling stations opened at 6:00 a.m. local time and were scheduled to close at 6:00 p.m. with a national holiday declared to maximize turnout among more than 40 million registered voters.
Park commands broad support from the older Koreans in their 50s and 60s, while Moon has strong support from younger Koreans, according to news agency reports.
Seven hours after the polls opened at 6 a.m., election officials reported an average voter turnout of 45.3 percent nationwide, higher than 36.7 percent and 41.9 percent reported at the same time in the previous presidential polls in 2007 and 2002, respectively, Yonhap news agency stated.
People lined up to vote despite a strong cold wave that pulled down temperatures to as low as minus 10.3 degrees Celsius in Seoul.
Election experts believe that the relatively higher voter turnout means more young voters participated in the balloting, thus giving Moon a greater advantage.
Local television stations are expected to announce the results of the joint exit polls at 6 p.m. A better prediction of the outcome is expected within a few hours of the ballot counting process later in the day with the winner likely to emerge after 11 p.m. at the earliest, Yonhap reported.