South Korea's ruling conservative party has suffered an upset defeat in the country's parliamentary election.

President Park Geun-hye's Saenuri Party took less than half of the 300 National Assembly seats. Party chief Kim Moo-sung has resigned, saying he will take responsibility for the defeat.

Meanwhile, the main opposition Minjoo Party edged out the ruling party by one vote, becoming the majority. The loss by President Park's party means her government will face more obstacles as she tries to push through her legislative agenda to boost a sluggish economy.