South Koreans flocked to polling stations to elect a new leader on Tuesday, with a high turnout suggesting voters are eager to move on from a corruption scandal that brought down the former president and shook the political and business elite.

Unless there is a major upset, liberal Moon Jae-in - who calls for a moderate approach on North Korea, wants to reform powerful family-run conglomerates and boost fiscal spending to create jobs - will be elected president.

The vote will end a months-long leadership vacuum. Former president Park Geun-hye was ousted on charges of bribery and abuse of power in March to become South Korea's first democratically elected president to be thrown out of office.

Park is in jail, on trial, but denies any wrongdoing. She had decided not to cast a vote, South Korean media reported.

The National Election Commission said turnout was 67.1 percent by 4 p.m. (0700 GMT), exceeding the 65.2 percent at the same time in the previous presidential election, in 2012.

The commission expects final turnout of more than 80 percent, which would be the highest since President Kim Dae-jung was elected in 1997, when 80.7 percent of voters cast ballots.

The Democratic Party's Moon, who lost narrowly to Park in 2012, has criticised the two former conservative governments for failing to stop North Korea's weapons development. He advocates a two-track policy of dialogue while maintaining pressure and sanctions to encourage change.

He said in a YouTube live stream on Tuesday that South Korea should take on a more active diplomatic role to curb North Korea's nuclear threat and not watch idly as the United States and China talk to each other.

STRAIGHT TO WORK

A Gallup Korea poll last week showed Moon had 38 percent support in a field of 13 candidates, with centrist Ahn Cheol-soo his nearest challenger on 20 percent.

The winner was expected to be sworn in on Wednesday after the release of the official result. Most candidates, including Moon and Ahn, have said they would skip a lavish inauguration ceremony and start work straight away.

Moon said he had "poured every last drop of energy" into the campaign, reassuring voters he was in good health despite sporting bruises on his hands and arms from being jostled in crowds during campaigning.

"What are a few bruises?" he said.

A quarter of voters cast ballots early last week, a figure seen driven higher by the participation of younger people.

Polls will close at 8 p.m. (1100 GMT), two hours later than in 2012.

Moon says he would want to be approachable and move freely among the people, even though many thought that "unrealistic".

"I want to ease up the protection detail on the president, go to and from work with the people and mingle with people after work - I fully believe I can do this," he said.

A Moon victory would be expected to improve market sentiment at a time when exports are supporting an economic recovery in Asia's fourth largest economy.

The new leader is expected to quickly name a prime minister, who will need parliamentary approval, and main cabinet positions, including national security and finance ministers, which do not need parliamentary confirmation.

CHINA URGES DIALOGUE

The election is being watched closely by allies and neighbours at a time of high tension over North Korea's accelerating development of weapons. Pyongyang carried out its fifth nuclear test in September and is believed to be readying for another.

U.S. President Donald Trump has vowed to stop North Korea developing a nuclear missile that can hit the United States.

The new president will also have to face an angry China, which objects to South Korea's decision to deploy a U.S. anti-missile defence system, known as THAAD, that China sees as a threat.

China's official Xinhua news agency said in a commentary on Tuesday a new South Korean leader should "demonstrate its readiness to ease tensions" by calling off deployment of the THAAD, "which has proved useless in thwarting Pyongyang's nuclear and missile activities".

"It would be advisable that the next South Korean leader respond positively to China's proposal to resume dialogues - Pyongyang suspends its nuclear programme in exchange for the U.S.-South Korean halt of military exercises - something the previous South Korean leaders have failed to do in the past 10 years," Xinhua said.

Japan's Chief Cabinet Secretary Yoshihide Suga told a regular news conference the relationship between South Korea and Japan would develop regardless of who became president.

"Collaboration between Japan and South Korea is quite important for responding to the North Korean problem and for the peace and stability of the region," he said.

North Korea would be keen to see a Moon victory. Its official Rodong Sinmun newspaper said on Tuesday conservative rule in the South should be "buried in the grave of history".

"Cleanly eradicating the puppet conservative group that has committed intolerable crimes is the shortcut to new politics, new life and a new world," it said.

The U.S. State Department said Washington looked forward to continuing "close, constructive, deep cooperation". The United States has about 28,500 troops in South Korea.

"We will continue to meet all our alliance commitments, especially with respect to defending against the threat from North Korea," State Department spokeswoman Katina Adams told the Yonhap News Agency.