The anti-corruption agency said it will ask the court to extend the jail term of the president who did not accompany him to 20 days.
South Korean anti-corruption investigators said they will request an extension of President Yoon Suk-yeol's detention after the impeached leader refused to be questioned again over his short-lived declaration of martial law.
South Korea's corruption investigation office (CIO) said on Friday it would ask the court to approve an extension of Yoon's jail term by 20 days.
Yoon on Wednesday became the first president in South Korean history to be arrested after a dawn search at his home in Seoul.
Under the decision handed down on Wednesday, investigators were given the power to detain the leader for up to 48 hours.
The High District Court in Seoul on Thursday rejected a request from Yoon's lawyers to challenge his arrest, which followed a long standoff between investigators and the president's security at his court.
Yoon, who has been suspended from office since his impeachment on December 14, is being investigated on charges that include terrorism, which carries a life sentence or the death penalty, although South Korea has a long statute of limitations on the death penalty.
Yoon's future in office is being reviewed separately by the Constitutional Court, which has 180 days to decide whether to approve his impeachment by the National Assembly.
Finance Minister and Deputy Prime Minister Choi Sang-mok is serving as president, after Yoon's successor, Han Duck-soo, was also impeached for refusing to fill three seats on the Supreme Constitutional Court.
Yoon's legal team, which said his arrest was illegal, said the president saw no reason to answer questions.
“The president will not appear at the CIO today. He has fully explained his investigation on the first day,” Yoon's lawyer, Seok Dong-hyeon, told reporters.
Despite Yoon's legal troubles, the next leader of the People Power Party (PPP) rose to the polls amid major divisions over his arrest.
In a Gallup Korea poll released Friday, the PPP became more popular than the main opposition Democratic Party for the first time since August, gaining the approval of 39 percent of respondents compared to 36 percent of its leftist counterpart.