South Korea's ruling party leader called on President Yoon Suk Yeol to resign Friday over his attempt to impose martial law, warning that he poses a grave danger to the country.

Han Dong-hun, leader of the People's Power Party (PPP), said he had received information that Yoon had ordered the country's defense counterintelligence commander to arrest and detain unspecified key politicians on charges of "anti-state activities" under martial law.

Han's comments almost guarantee that enough lawmakers will vote to impeach the president on Saturday. Yoon's impeachment would require the support of at least two-thirds of the National Assembly, or 200 of its 300 members.

The opposition parties that jointly submitted the impeachment motion have a combined total of 192 seats. Meanwhile, Han leads an anti-Yoon faction within the ruling party, and 18 lawmakers in his faction voted with opposition lawmakers to overturn Yoon's martial law decree.

Hundreds of citizens participated in a candlelight vigil, condemning President Yoon Suk-yeol's declaration of martial law and calling for his resignation. (Image: Chris Jung/NurPhoto/picture alliance via Deutsche Welle)

Han's unexpected U-turn

Han's comments were a reversal from Thursday, when he said he would block the impeachment and another party leader insisted that all 108 members of the PPP would unite to support Yoon in Saturday's vote.

However, Han said Friday that Yoon poses a "significant risk of extreme actions, like reattempting to impose martial law, which could potentially put the Republic of Korea and its citizens in great danger."

He also said that Yoon's refusal to admit that he did anything wrong in declaring martial law Tuesday night prompted his change of position.

"Considering the newly emerging facts, I believe that a swift suspension of President Yoon Suk Yeol's duties is necessary to safeguard the Republic of Korea and its people," Han said.

Prosecutors to investigate rebellion charges

Meanwhile, Prosecutor General Shim Woo Jung told reporters Friday that prosecutors plan to investigate rebellion charges against Yoon following complaints from the opposition that his actions amounted to a "self-coup."

While the president largely enjoys immunity from prosecution while in office, the protection does not extend to charges of rebellion or treason. It wasn't immediately clear how prosecutors plan to proceed with an investigation into Yoon.

If Yoon is impeached on Saturday, he would be suspended until the Constitutional Court decides whether to remove him from office or restore his presidential powers. Prime Minister Han Duck-soo would assume presidential duties.

Police said they expect tens of thousands of South Koreans to attend rallies in Seoul on Saturday ahead of the impeachment vote.

"A large-scale gathering and march involving tens of thousands of participants will be held in the city center and Yeouido area (in Seoul) on Saturday, and traffic restrictions will be imposed on some roads," Seoul Metropolitan Police said in a statement.

The Defense Ministry, meanwhile, said it had suspended three senior commanders involved in the martial law operation.

"The Ministry of Defense has executed the separation and suspension of duties for three key position holders ... related to the current situation as of December 6," the ministry said in a statement.

US' Blinken reaffirms Washington's commitment

Amid concern in Washington at events unfolding in South Korea, a major Asian ally of the US, US Secretary of State Antony Blinken has said he is confident of the country's "democratic resilience."

Blinken "spoke with Foreign Minister (Cho Tae-yul) following deeply concerning developments in (South Korea)," State Department spokesman Matthew Miller said on social media platform X.

"He welcomed the lifting of martial law, expressed confidence in the country's democratic resilience, and reaffirmed the United States' ironclad commitment to our Alliance," the post continued.