South Korean President Lee Myung-Bak suffered a setback to his hardline policy on North Korea and domestic reform agenda Thursday, with voters turning against his party in local elections.

Results from Wednesday's vote showed Lee's Grand National Party (GNP) secured only six out of the 16 posts for provincial governors or city mayors nationwide, according to the National Election Commission.

The elections for 4,000 posts including provincial governors, mayors and councillors were widely seen as a mid-term referendum on Lee's leadership and a key gauge for public sentiment ahead of the 2012 presidential contest.

The main opposition Liberal Democratic Party (DP) took seven mayoral or gubernatorial posts, independent candidates won two and the minor opposition Liberty Forward Party (LFP) grabbed one, the election commission said.

The GNP won 12 of the 16 seats four years ago and party chairman Chung Mong-Joon offered his resignation, taking responsibility for the losses.

"I did my best but failed to win the heart of the people," Chung told a meeting with party officials. "I feel responsible as the one who headed the party's election committee. I hereby express my intent to resign."

President Lee's chief secretary, Chung Chung-Kil, also offered to resign over the ruling party's poor election results, officials said.

Lee took office in February 2008 for a single five-year term and angered North Korea by scrapping the decade-long "Sunshine" aid and engagement policy of his DP predecessors.

The opposition has tried to draw attention to Lee's 19-billion-dollar project to dredge, deepen and dam four major rivers, which has sparked protests from environmentalists and questions about its value.

The sinking of a South Korean warship in March with the loss of 46 lives cast a long shadow over the nationwide elections.

GNP candidates were re-elected as mayor of Seoul and governor of Gyeonggi Province surrounding the capital city in a tight race with opposition rivals.

Security concerns against North Korea over the sinking of the 1,200-ton Cheonan corvette had been expected to overshadow the public debate over Lee's policy fumbles for the ruling party's sake.

"The ruling party tried to cover up other policies with the security problem, and used the Cheonan incident in politics but obviously, it was not successful," Park Kie-Duck of private think Sejong Institute told AFP.

"Without the Cheonan incident, the opposition party would have won in Seoul as well."

Park said he expects the Lee government can no longer promote such a controversial project as the huge civil engineering work in the major rivers.

- AFP