SEOUL (THE KOREA HERALD/ASIA NEWS NETWORK) - South Korean presidential front-runner Moon Jae In of the liberal Democratic Party appeared with his wife at a polling station in Seoul to cast their votes for the Blue House election on Tuesday (May 9), after which he posed for selfies with his supporters.

Moon and his wife, Kim Jung Sook, cast their ballots at the Hongeun Middle School in Seodaemun-gu, Seoul, early Tuesday.

Wearing a blue suit with a white shirt, Moon arrived at the school gate at 8.35am local time. The venue was already crowded with citizens and reporters, trying to catch a glimpse of the presidential favourite.

"Only voting can change the reality," he said after he came out from the polling station building. "Please bring together the strength to build a proper country."

Moon pledged to bring together the divided political forces across the country and cooperate with rivals to mend the cracks.

Moon's supporters and ordinary citizens who came to vote at the polling station cheered and took selfies with him as he headed out of the school grounds, with some of them shouting: "Make Korea a good country, a proper nation."

Some asked for his autograph on their smartphones and T-shirts.

One supporter, Song Nan Young, came from Bucheon, south of Seoul, to cast her ballot at 6am at the school.

She said she had travelled for an hour and a half from her home to see Moon in person. The 34-year-old company worker said she was "sure he will do a good job as president".

Moon has consistently topped local polls, with support ratings ranging from 35 to 40 per cent.

His runner-up rivals -Hong Joon Pyo of the Liberty Korea Party, Ahn Cheol Soo of the People's Party, Yoo Seong Min of the Bareun Party and Sim Sang Jeung of the Justice Party - also cast their vote in their respective constituencies early in the day.

Moon, 64, later went back to his home, his campaign aide said. He is expected to head to the National Assembly later in the day to monitor the election outcome from there.