Democratic Party candidate Moon Jae-in will become the next president of South Korea after winning Tuesday's election, ending a decade of conservative rule. 

Moon collected 41.1 percent of the vote, according to official figures - way ahead of conservative Hong Joon-Pyo's 24 percent and centrist Ahn Cheol-Soo's 21.4 percent.

Moon was due to take the oath of office on Wednesday and to then announce major cabinet and presidential staff appointments. His five-year term will end a power vacuum following the March dismissal of President Park Geun-hye.

Voter turnout was high as South Koreans appeared keen to move on after a corruption scandal shook the country to its foundations. Park was thrown out of office on charges of bribery and abuse of power.

Korean news agency Yonhap put the turnout at 75 percent of 42.5 million registered voters, citing the National Election Commission an hour before the polling stations closed.

Moon was expected to forgo an elaborate inauguration ceremony.

"I will make a just, united country," Moon told a crowd just before midnight. "I will be a president who also serves all the people who did not support me."

On the domestic front, the 64-year-old Moon plans to reform the country's powerful family-run businesses and boost fiscal spending

Moon is also likely to shake up Seoul's relations with North Korea by pushing for greater engagement instead of confrontation. This could also see a change in approach in how South Korea interacts with its ally, the United States, which has signalled a more confrontational policy towards Pyongyang over its ballistic missile and nuclear weapons program. 

Moon, who narrowly lost to Park in 2012, would also need to face the growing youth unemployment and rising household debt during his five year-term.

There will be no traditional two month transition period because it was a by-election to replace Park. 

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cw,aw/kms (AP, Reuters, dpa)