SEOUL (Yonhap) – The ruling and main opposition parties were running neck-and-neck in Wednesday's local elections, with the results of four key battlegrounds appearing likely to determine the winner.

As the first nationwide elections under President Park Geun-hye, the polls were seen as a crucial test of public support for the conservative administration that has drawn fire for its botched handling of a deadly ferry sinking in April. Park took office in February 2013.

The elections for a total of 3,952 officials, including 17 metropolitan mayors and provincial governors and 226 heads of low-level administrative units, as well as local council members and education superintendents, were the first nationwide polls in 18 months.

As of 9:50 p.m., the ruling Saenuri Party was set to win five of the 17 metropolitan mayoral and gubernatorial seats up for grabs, while the main opposition New Politics Alliance for Democracy (NPAD) appeared certain to win three, according to the National Election Commission (NEC).

Of the five seats likely to go to the ruling party, two were for the mayors of Daegu and Ulsan, while the remaining three were for the governors of South and North Gyeongsang provinces and Jeju Province, the NEC said.

NPAD, meanwhile, is expected to score victories in its traditional strongholds of the city of Gwangju and South and North Jeolla provinces.

The race was too close to call in four regions -- Incheon, Daejeon, Gyeonggi Province and North Chungcheong Province.

In the race for Gyeonggi governor, with 3.5 percent of the ballots counted, ruling party candidate Nam Kyung-pil won 52.9 percent against 47.1 percent for his NPAD rival Kim Jin-pyo.

With 1.84 percent of the votes counted in the Incheon mayoral race, Yoo Jeong-bok of the ruling party held 49.8 percent against 48.4 percent for Song Young-gil of the opposition party.

One of the most watched contests was the mayoral race in Seoul.

With only 0.9 percent of the ballots counted, current Mayor Park Won-soon of NPAD led his rival Chung Mong-joon of the Saenuri Party by a wide margin, winning 59.5 percent of the vote against Chung's 39.8 percent.

Voting took place from 6 a.m. to 6 p.m. at 13,665 polling stations nationwide, drawing 56.8 percent of eligible voters, according to a preliminary count by the NEC. The turnout was the highest for nationwide local elections since the first such polls in 1995 when it reached 68.4 percent.

Ballot boxes were sealed as soon as voting closed and taken to 252 counting offices for tallying.

Some 41.29 million people, or 80.4 percent of the country's population of 51.33 million, were eligible to vote, according to the NEC.