This handout from the South Korean Presidential Office via Yonhap taken and released on December 14, 2024 shows President Yoon Suk Yeol giving a public address from his official residence in Seoul. South Korean Presidential Office via Yonhap/AFP

SEOUL, South Korea -- South Korea's opposition leader urged a top court on Sunday to swiftly formalize the impeachment of President Yoon Suk Yeol and ease the "suffering of the people" after his short-lived martial law decree.

Lawmakers voted on Saturday to remove Yoon from office over his "insurrectionary" suspension of civilian rule, which plunged South Korea into some of its worst political turmoil in years.

Yoon has been suspended while South Korea's Constitutional Court deliberates, with Prime Minister Han Duck-soo serving as interim leader.

The court has 180 days to rule on Yoon's future.

But opposition leader Lee Jae-myung on Sunday urged the judges to "swiftly" remove Yoon from office.

"This is the only way to minimize national turmoil and alleviate the suffering of the people," he said.

"To hold those responsible for this absurd situation accountable and to prevent its recurrence, it is essential to uncover the truth and demand accountability."

READ: South Korean lawmakers impeach President Yoon over martial law bid

An investigation into Yoon's inner circle over last week's martial law declaration has also rumbled on.

On Sunday, prosecutors said they were seeking an arrest warrant for the head of the Army Special Warfare Command Kwak Jong-keun, Yonhap news agency said.

Kwak is accused of sending special forces troops to the country's parliament during the failed martial law bid -- sparking a dramatic confrontation between soldiers and parliamentary staff.

And on Saturday, police arrested Yeo In-hyung, head of the Defense Counterintelligence Command, on charges including insurrection.

READ: Tears of joy, K-pop on Seoul streets as Yoon impeached

- 'Resiliency of democracy' -

The South Korean government has meanwhile sought to project an air of business as usual.

Acting president Han on Sunday held a call with US President Joe Biden, who underscored the strength of bilateral ties.

The United States is a key treaty ally of Seoul's, stationing around 28,000 troops in South Korea.

The White House said in a readout that Biden had expressed "confidence that the Alliance will remain the linchpin for peace and prosperity in the Indo-Pacific region during Acting President Han's tenure".

"President Biden expressed his appreciation for the resiliency of democracy and the rule of law in the Republic of Korea," the White House said.

Han has also ordered the military to "enhance vigilance" against North Korea, with which the South remains technically at war.

North Korea is yet to publicly comment on Yoon's impeachment.

Vast protests both for and against Yoon have rocked the South Korean capital since the December 3 martial law decree.

Demonstrators in both camps have vowed to keep up the pressure campaign as the Constitutional Court mulls Yoon's fate.

"I will certainly protest at the court to demand it reject the impeachment," Cho Hee-sun, a Yoon supporter, told AFP at a rally on Saturday before the parliamentary vote.

Seoul police estimated at least 200,000 people had gathered outside parliament in support of removing the president.

© Agence France-Presse