The conservative party of South Korea's new president won a slim a majority in a Wednesday parliamentary election, which should give him the political muscle to push through reforms for Asia's fourth largest economy.

But it is not the commanding lead President Lee Myung-bak might have hoped for after he took office in February, intent on radical changes to how the government manages an export-driven economy that faces increasingly tough competition from its neighbours.

"I believe the voters made a political decision to give us a stable majority for the reason they elected President Lee Myung-bak, which is to revive the economy," head of the conservative Grand National Party (GNP), Kang Jae-sup said in a TV interview.

According to National Election Commission preliminary results, the GNP won 130 of the 245 constituencies being contested.

TV network projections said the group will win enough of the remaining 54 seats through proportional representation to capture a total of about 152-154 seats in the 299-seat National Assembly.

Lee began his five-year term in February pledging to boost growth this year to 6 percent from 5 percent last year, cut the red tape stifling business, win approval for a trade deal with major ally the United States and open the economy more to foreign investment.

The projected GNP win marked the end of a string of victories for liberals in parliamentary races since the country began open, democratic elections 20 years ago.

But to bolster his grip on power, Lee may need to call on other conservative stalwarts who bolted from the faction-ridden GNP in anger at his leadership and are expected to win just over 30 seats.

The left-of-centre United Democratic Party (UDP) is headed for a crushing defeat, with projections saying it could see its seats cut by about 40 percent from its current 136 to about 80.

To add to its misery, both the party leader Sohn Hak-kyu and the liberal candidate for the presidential election Chung Dong-young appeared headed for defeat.

Official results are expected in the early hours of Thursday. The new parliament will sit in late May and serve for four years.

Communist North Korea turned up the heat ahead of the race with threats and taunts. On Tuesday, it branded Lee a traitor, saying his demands for the impoverished state to change its ways were pushing the Korean peninsula back to war.

But voters, accustomed to years of fiery anti-South rhetoric, appeared to ignore the latest barbs from its irritable neighbour in a campaign largely devoid of debate on any serious issue.

The National Election Commission said the turnout was expected to be a record low of 46 percent even though it tried to entice voters with discount vouchers for parks and museums as well as with an ad campaign featuring a highly popular song-and-dance group of teenagers called the "Wonder Girls".

Lee had been hoping to carry the support from his landslide victory in December to the National Assembly race but has seen his high popularity slip as his government stumbled out the blocks and bungled personnel appointments.

The damage from a global downturn began to look far more serious for South Korea just as he took office, with some analysts calling his economic growth target far too optimistic.