South Korea's impeached President Yoon Suk Yeol on Wednesday yet again defied summons from investigators who are probing events leading up to the short-lived December 3 martial law, YonhapNews reported.

It was the third time Yoon, 63, refused to attend questioning.

Facing charges of insurrection and treason, he remains suspended from office after parliament impeached him on December 14 and awaits trial by the Constitutional Court, which will hold its first hearing on Friday.

Yoon was asked to appear for questioning before a joint team of investigators from the Corruption Investigation Office for High-ranking Officials (CIO), police and the Defence Ministry in Gwacheon, south of the capital Seoul.

The CIO plans to wait for Yoon's possible appearance later in the day. If he does not show up, the team is expected to decide as early as Thursday on further possible measures, such as sending summons for the third time or seeking an arrest warrant.

Earlier, Yoon refused to attend a summons by the CIO last week, and another such call by prosecutors.

In the absence of Yoon, the state affairs are run by acting president and Prime Minister Han Duck-soo.