• South Korea's president is facing calls from his own party for his impeachment.
• He declared martial law on Tuesday evening, only to backpedal six hours later.
• Yoon tried to arrest top lawmakers during that period, his party's leader said on Friday.

South Korea's president, Yoon Suk Yeol, is facing calls from his own party for his immediate removal after his short-lived declaration of martial law.

Han Dong-hoon, the leader of the conservative People Power Party, told local media on Friday in Seoul that Yoon had ordered the arrest of top lawmakers after he announced martial law.

"Given the newly revealed facts, I believe it is necessary to promptly suspend President Yoon Suk Yeol from his duties to protect the Republic of Korea and its people," Han said, per a translation by the Yonhap news agency.

Han added that he was concerned Yoon would take more "radical" action if he remained in power.

He told local media that leaders had learned on Thursday that Yoon instructed the country's intelligence commander to detain politicians during martial law.

According to Han, Yoon had called them "anti-state" forces.

Yoon had used the same term to describe his political rivals when he made his shock announcement on Tuesday evening, accusing South Korea's opposition of being affiliated with North Korea as justification for martial law.

His declaration, made at around 10:27 p.m. Seoul time, was instantly denounced by Han and the leader of the opposition party, Lee Jae-myung.

They summoned their party members to the National Assembly, where they voted to lift martial law before troops could enter the main hall.

Of the 300-seat National Assembly, 190 members were present that night. They voted unanimously against Yoon's decision. Yoon lifted martial law at about 4:30 a.m. local time.

Impeachment for Yoon looms

Lee's main opposition party, the Democratic Party, has held a majority through 170 seats since the legislative elections in April and has stymied Yoon's parliamentary moves since.

The ruling People Power Party, of which Yoon is a member, holds 108 seats.

Yoon now faces impeachment through a motion filed by the Democratic Party, which must pass a vote in the National Assembly.

Han's ruling party initially stayed out of proceedings and was expected to oppose impeachment. But with support from smaller opposition parties, the Democratic Party only needs eight members of the ruling party to meet the required 200-vote threshhold.

With Han now calling for Yoon's removal, it's more likely those eight votes will come through.

If successful, the motion will suspend the president as a trial against him proceeds in the constitutional court.

Should two-thirds of the court's nine-member council see fit to impeach him, Yoon will be removed, and a replacement must be elected within 60 days.

The South Korean won weakened immediately after Yoon declared martial law to about 1,440 against the US dollar but recovered to 1,420 on Wednesday, a difference of 1.4% from the day before.