SEOUL, South Korea (AP) — South Korea's opposition leader questioned the state of mind of President Yoon Suk Yeol and vowed to make all-out efforts to get him impeached soon, saying Friday that Yoon's controversial martial law imposition this week showed he could make other extreme moves on vital issues.

South Korea's main opposition Democratic Party leader Lee Jae-myung, speaks during an interview with The Associated Press at the National Assembly in Seoul, South Korea, Friday, Dec. 6, 2024. The letters read "Yoon Suk Yeol." (AP Photo/Lee Jin-man)

"A more dangerous part of the martial law case is the state of mind of the president who decided to do something that no one understands, rather than the fact that he did it," Lee Jae-myung, leader of the liberal opposition Democratic Party, told The Associated Press in an interview.

"There is a high possibility that he could do totally incomprehensible things on security, defense, economy and foreign affairs issues."

Yoon's controversial martial law imposition on Tuesday night lasted only six hours before it was overturned by the opposition-controlled parliament in a unanimous vote and was lifted by Yoon before daybreak Wednesday. But the short-lived declaration is threatening to plunge the country into a political turmoil and tarnishing its international image.

In his martial law announcement, Yoon cited the need to eliminate "shameless North Korea followers and anti-state forces." But it's still unclear why Yoon pressed ahead with martial law when it was obvious that it would be rejected by the National Assembly. Some experts say Yoon likely hoped to divert public attentions away from a spate of scandals involving himself and his wife.

In response to questions by the AP about Lee's comments, the presidential office said that Yoon has no problems in handling state affairs and making decisions and he is performing his duties normally.

Yoon hasn't made any public appearance since he announced he was lifting martial law, though his office said Thursday the president replaced his defense minister, who was believed to have recommended the martial law decree to Yoon.

Lee's Democratic Party and other small opposition parties are pushing for a parliamentary vote on an impeachment motion on Yoon on Saturday to suspend his presidential power and responsibility. They call Yoon's martial law "unconstitutional, illegal rebellion or coup."

But they need backing from some members of the governing People Power Party to reach the two-thirds majority required to pass the impeachment motion. If approved, the Constitutional Court is to determine whether to remove him from office or restore his presidential power.

Opinion surveys showed that Lee, who lost the 2022 presidential election to Yoon by a razor-thin margin, is the favorite to succeed Yoon in the 2027 race, despite facing several court trials over corruption and other charges.

Earlier Friday, Han Dong-hun, leader of the ruling People Power Party, raised the need to suspend Yoon's presidential power swiftly, saying he poses a "significant risk of extreme actions, like reattempting to impose martial law." Han earlier said his party would oppose the passage of Yoon's impeachment motion to prevent social chaos.

Lee said his party has been contacting and persuading PPP members to join opposition parties' efforts to impeach Yoon. He downplayed the significance of Han's comments, saying it will likely be "his individual opinion." Lee noted that PPP's official position remains unchanged.

Han leads a minority faction within PPP whose 18 lawmakers voted down Yoon's martial law declaration together with opposition lawmakers.

Lee said that prospects for the impeachment motion's passage is "fluid." But he said the ruling party wouldn't survive if it makes a decision that goes against public sentiment. A survey released Thursday indicated that more than 70% of South Koreans support Yoon's impeachment, while another survey published Friday put Yoon's approval rating at 16%, the lowest since he took office in May 2022.

Lee argued that Yoon has already virtually lost authority as president so that he is unable to govern the country and will only likely opt for other drastic steps to avoid crises.

"Thus, it's necessary to mobilize all available methods and capabilities to suspend Yoon at the earliest possible time," Lee said.

Opposition parties could submit a new impeachment motion if the current one is voted down. Lee said public support of Yoon's impeachment motion would eventually result in making the ruling party back the motion.