SEOUL (Kyodo) -- The chief of South Korea's ruling People Power Party said Friday it is necessary to immediately suspend President Yoon Suk Yeol's powers, following his short-lived declaration of martial law that was met with public condemnation.

Han Dong Hoon, who said the previous day that the party would seek to prevent the passage of an impeachment motion against Yoon, now appears inclined to support it, though he did not mention the motion during a party meeting on Friday morning.

Han said credible sources confirmed Thursday night that Yoon had ordered the arrest and detention of key politicians, labeling them as anti-state forces, after he declared martial law.

"Considering the newly uncovered facts, I believe that it is necessary to urgently suspend President Yoon Suk Yeol from performing his duties to safeguard the Republic of Korea and its people," Han said, using South Korea's official name.

The presidential office said later that day that Yoon did not order the arrest or detention of any politicians, according to local media reports.

The impeachment motion was submitted by the main opposition Democratic Party, which holds a majority in the National Assembly, and five other parties Wednesday.

After the PPP meeting, one of its lawmakers, Cho Kyoung Tae, told reporters he supports impeaching Yoon, according to a Yonhap News Agency report, the first ruling party member to publically back it.

Impeachment requires support from two-thirds of the 300 members of the unicameral legislature, which means at least eight votes from the ruling party are needed.

The National Assembly's vote on impeachment, expected for around 7 p.m. on Saturday, could be held earlier, possibly later Friday, according to local media reports.

When asked whether the parliamentary vote on impeachment should be held as early as Friday, Cho said "Yes."

At a DP meeting Friday, leader Lee Jae Myung stressed the urgency of preventing Yoon from wielding his powers, saying "We cannot entrust the governance of the nation, even for a moment, to a president who has endangered the lives of the sovereign people through unconstitutional and illegal actions."

Yoon allegedly failed to meet constitutional requirements when he declared martial law, which only lasted six hours from late Tuesday before being rescinded.

After martial law was declared, soldiers were sent to the parliament building but were withdrawn after lawmakers passed a resolution to lift the declaration.

South Korea's Supreme Prosecutors' Office said Friday that it had formed a special team to investigate the procedure followed by Yoon when he declared martial law.

The defense ministry said it will fully cooperate with the prosecutor's investigation and deploy military prosecutors to facilitate a joint investigation.

Defense Minister Kim Yong Hyun, who reportedly suggested the declaration to Yoon, resigned Thursday to take responsibility for the situation.

Acting defense minister Kim Seon Ho said in a briefing Friday that the ministry and military will not act in support of another declaration of martial law, responding to speculation they could do so again.

Prosecutors imposed a travel ban on Kim Yong Hyun on Thursday after a group of minor political parties filed a complaint that he, Yoon, and Army Chief of Staff Gen. Park An Su committed treason in conspiring to declare martial law, Yonhap News Agency reported.