The South Korean leader is barred from foreign travel as part of a probe into his inner circle over the dramatic events of December 3-4 that stunned Seoul's allies and threw the country into some of its deepest political turmoil in years.

Yoon, staring down an impeachment vote in parliament on Saturday, vowed to "fight with the people until the very last minute".

"I apologize again to the people who must have been surprised and anxious due to the martial law," he said in a televised address.

"Please trust me."

Saturday's impeachment vote will take place at around 5:00 p.m.

It needs to win support from eight members of the ruling People Power Party (PPP) to secure the necessary two-thirds majority.

PPP leader Han Dong-hoon urged party members on Thursday to attend the meeting and vote "according to their conviction and conscience".

That came as police attempted another raid on Yoon's presidential office compound, Yonhap news agency reported, a day after a similar attempt was blocked by security guards.

The main opposition Democratic Party has said it would file legal complaints for insurrection against the president's staff and security if they continued to obstruct law enforcement.

Yonhap said Thursday's raid focused on the headquarters of the military's Joint Chiefs of Staff, which reportedly agreed to cooperate with the investigation.

South Korea's capital has been rocked by daily protests since last week, with thousands gathering to demand Yoon's resignation.

Members of Yoon's inner circle have come under intense scrutiny for their alleged role in last week's martial law declaration.

Police said on Thursday they had raided the headquarters of the military's capital defense command, which was deployed during the martial law declaration.

Former defense minister Kim Yong-hyun, who is accused of urging Yoon to impose martial law, tried to kill himself in prison on Tuesday, authorities said. 

Kim was first detained on Sunday and later formally arrested on charges of "engaging in critical duties during an insurrection" and "abuse of authority to obstruct the exercise of rights".

The former interior minister and the general in charge of the martial law operation are also barred from foreign travel.

Two senior police officials were also arrested early on Wednesday.

The PPP has said that, pending Yoon's resignation, he has agreed to hand power to Prime Minister Han Duck-soo and party chief Han.

But Yoon remained defiant on Thursday, accusing the opposition of pushing the country into a "national crisis".

"The National Assembly, dominated by the large opposition party, has become a monster that destroys the constitutional order of liberal democracy," Yoon said in his televised address.

But, he said, he would "not avoid legal and political responsibility regarding the declaration of martial law".

Yoon had said his declaration of martial law was intended, in part, to safeguard South Korea "from the threats posed by North Korea's communist forces and eliminate anti-state elements".