Han Duck-Soo announced his campaign to replace former president Yoon Suk-Yeol, who is impeached, in the June 3 election.

South Korea was sworn in as the third acting president in less than six months as his predecessor announced he was running for a quick election to replace former impeacher leader Yoon Suk-Yeol.

Education Minister Lee Ju-ho promised to ensure "stability" as he was appointed acting leader on Friday, the day after Prime Minister Han Duck-soo resigned in the June 3 general election.

Li told reporters: "I will try my best to ensure the stable management of the government's functions."

The appointment of a new acting president is because Han's campaign has injected more uncertainty into the election race, which is skeptical of the qualification of Democratic left-leading leader Lee Jae-Myung.

"I am determined to find the Republic of Korea I love and the future of all of us," Han said at a press conference in the National Assembly on Friday.

“I will do my best to be elected by the people in this presidential election.”

On Thursday, the Supreme Court overturned Lee Jae-Myung's acquittal of the election law violation and sent the case back to the lower court.

If he insisted on his beliefs before the election, Lee ruled for months of polls and would be disqualified from the competition.

Next month's election was called up after former prosecutor-turned conservative politician Yuan, who was removed from office after he was shocked in December's announcement of martial law.

Yoon's declaration lasted less than six hours before being voted by the South Korean legislature, but political uncertainty and chaos continued to reverberate nearly six months later.

Han, 75, took over as acting president after Yoon's impeachment on December 14, and was then replaced by Finance Minister Choi Sang-Mok.

In March, the Constitutional Court overturned South Korea's impeachment, reinstating his role as an acting leader.

Han is a veteran politician and bureaucrat who served as prime minister in liberal and conservative governments, as Secretary of Trade, Treasury and U.S. Ambassador.

Although not affiliated with the political party, Han is expected to form an alliance with Yin's conservative People's Power Party.

He said his campaign platform will focus on limiting the power of executives and amending the constitution to add more checks and balances.

After Han's announcement, the Democrats accused him of giving up his duty as a caretaker leader.

"We warn former Prime Minister Han. Don't hide your greed with your lies you are running for the people," Democratic spokesman Noh Jong-Myun said.