Il Nuovo Postiglione - South Korea's new President Lee takes power after sweeping election win

Lee won a thumping victory over conservative Kim Moon-soo, of disgraced ex-president Yoon Suk Yeol's former party, with his term begining immediately after the National Election Commission certified the vote tally early Wednesday.

In a regular presidential election, South Korea allows for a months-long transition period -- but as Lee's victory came in a snap election after Yoon's impeachment, his term began right away.

"The National Election Commission hereby declares Lee Jae-myung of the Democratic Party as the elected president," National Election Commission chairperson Roh Tae-ak said early Wednesday.

Kim had conceded hours earlier, as final votes were still being counted. Official results showed he had no chance of winning.

Lee assumes office with a bulging in-tray, from sluggish growth and a global trade war to mounting concerns over military ties between nuclear-armed Pyongyang and Moscow.

He also faces the challenge of leading a nation still reeling from the turmoil sparked by Yoon's martial law declaration in December and the rise of the far right in its aftermath -- a development experts say has deeply shaken the country's collective sense of democracy.

In a speech to supporters early Wednesday, Lee urged South Koreans to move "forward with hope and make a fresh start from this moment on".

"Though we may have clashed for a while, even those who did not support us are still fellow citizens of the Republic of Korea," he said.

He also promised to "pursue dialogue, communication, and cooperation" with North Korea, with whom the South remains technically at war, "to find a path toward peaceful coexistence and shared prosperity".

Lee is expected to start his first day with a traditional phone briefing from the military's top commander, formally confirming the transfer of operational control of the country.

He is then likely to visit the National Cemetery, a longstanding tradition observed by his predecessors, including Yoon.

A modest inauguration ceremony will likely follow at the National Assembly -- the same site where Yoon deployed armed troops on the night he attempted to declare martial law.

- Blue House calling? -

It will be a muted affair with just a few hundred guests expected to attend, in contrast to the large outdoor events held after regularly scheduled elections, which often attract tens of thousands.

The new leader will then head to the presidential office to begin naming key cabinet members.

Disgraced ex-president Yoon moved the seat of power from the traditional Blue House to a hastily-converted government building in Yongsan, which Lee has previously said he would not use.

The focus will be on who is tapped to serve as presidential chief of staff, prime minister and director of the National Intelligence Service.

The day is expected to end with a flurry of congratulatory phone calls from world leaders, with US President Donald Trump likely to be the first on the line.

For many voters, like Noh Min-young, 20, who spent months in the street protesting Yoon's martial law declaration, the election was a relief and would allow the country to get back on track.

"I'm just glad now. There's no risk of the result being overturned, and the margin is enough not to lose momentum when it comes to clearing up the insurrection or implementing policies," she told AFP.

But experts warned that Lee's success in this election -- after he lost to Yoon in 2022 -- was due as much to his rivals' failings as his own strengths, with Kim hampered by political infighting and a fractured right wing vote, split by a third party candidate.

"Lee is expected to prioritize the alliance with the United States while simultaneously seeking engagement with both China and North Korea," he said.

That marks a departure from the policies of predecessors including Yoon, "who largely focused on North Korea and the United States, respectively."

D.Ricci--INP