Ruling New Frontier Party candidate Park Geun-hye holds a 0.5 percentage point lead, within the margin of error, over former human rights lawyer Moon Jae-in, according to the most recent opinion poll. A victory for Ms Park, the daughter of the country's longest-serving military dictator, Park Chung-hee, would make her South Korea's first female president.

''It's anybody's call,'' said Hahm Chai-bong, of the Asan Institute for Policy Studies in Seoul. ''At this point the turnout rate is everything.''

The National Election Commission said turnout was about 59 per cent on Wednesday afternoon, local time. Exit polls gave a slight edge to Ms Park.

The victor will take office in February when President Lee Myung-bak's five-year term ends.

A turnout above 70 per cent would indicate a large number of younger people going to the polls who are more likely to vote for Mr Moon, said Kim Ji-yoon, the Asan Institute's director of public opinion studies. ''Underneath the political apathy and general lack of voter participation, younger voters tend to be moderate, undecided or generally veer left of centre and support Moon,'' she said.

There is little to separate the candidates' economic policies. With voters demanding measures to reduce widening income disparity, Mr Moon and Ms Park have pledged to boost welfare spending, increase support for small and medium-sized businesses, and rein in the influence of family conglomerates known as chaebols. While the 10 largest chaebols, including Samsung, account for more than half of the total market capitalisation of the Korea Stock Exchange, the biggest 30 employ just 6 per cent of the workforce.

On North Korea, both candidates say they will unconditionally resume dialogue with Kim Jong-un's regime. BLOOMBERG, AFP