South Korea's third acting leader in five months, Lee Ju-ho, is an understated labour economist and education bureaucrat thrust into managing high-stakes trade talks with the United States and a country reeling from political knife fights before a crucial election.

South Korea’s acting leader, Prime Minister Han Duck-soo, says he is resigning amid reports he will run in next month’s presidential election.

Prime Minister Han Duck-soo has been mulling whether to contest the election, while the main opposition candidate and front-runner suffered a setback in court.