South Korea's anti-corruption agency will resume questioning President Yoon Suk Yeol on Thursday as part of a criminal probe into whether he committed insurrection, while the Constitutional Court holds a second hearing of the embattled leader's impeachment trial.

South Korea looks set for a dramatic political showdown this week as impeachment proceedings kick off against suspended President Yoon Suk Yeol, who remains holed up in his fortified residence evading arrest for a separate criminal investigation.

The second formal hearing of the impeachment trial is scheduled for 2 p.m., but Yoon's lawyers requested a postponement the previous day citing his detention and interrogation by investigators over his short-lived imposition of martial law.