Yoon had not appeared for questioning as of 10 a.m. on Christmas Day as requested by the Corruption Investigation Office for High-ranking Officials (CIO), after ignoring its first summons last week.

An agency official said it would continue waiting for Yoon on Wednesday, adding it would need to review the case further before seeking an arrest warrant, Yonhap news agency reported.

An official with a joint investigation unit, which the CIO is part of, told reporters later in the day that it had neither heard back from Yoon nor received a document for the appointment of his legal counsel as of 6 p.m. The unit would conduct a review and decide on further moves, the official said.

Yoon also did not respond on Dec. 15 to a separate summons by prosecutors who are investigating the martial law declaration, Yonhap said.

Seok Dong-hyeon, a lawyer and long-time friend of Yoon's, told reporters on Tuesday that it was unlikely that Yoon would appear for Wednesday's questioning, adding without elaborating that the conditions had not been met yet.

Yoon's repeated defiance of the summons and failures to appear for questioning have sparked criticism and calls from the opposition for his arrest, citing concerns over potential destruction of evidence.

In a televised address on Dec. 7, four days after the martial law declaration, Yoon said he would not evade legal and political responsibility for his actions.

He was impeached by parliament on Dec. 14 over his brief imposition of martial law and must now face a Constitutional Court trial on whether to remove him from office or restore his presidential powers.

Prosecutors, the police and the corruption investigation office have all launched probes into Yoon and other officials, seeking to pursue charges of insurrection, abuse of power or other crimes.

Insurrection is one of the few charges for which a South Korean president does not have immunity.

Seok has said Yoon is willing to present his views in person during legal proceedings related to the martial law declaration.