South Korean President Yoon Suk-yeol has made his first court appearance in the trial to determine the validity of his impeachment over his brief declaration of emergency martial law in December.

Yoon was arrested on Sunday on suspicion of orchestrating an insurrection.

On Tuesday, a Justice Ministry vehicle transported him from a detention center outside the capital, Seoul, to the Constitutional Court for the third hearing of the trial.

Yoon is the first South Korean president to attend his or her own impeachment trial.

At the start of the hearing, Yoon said he has lived with a firm belief in liberal democracy and asked the justices to consider his case thoroughly as the court is an institution that exists to defend the Constitution.

Representatives from the National Assembly, which voted to impeach Yoon, argued that the president's allegations of electoral fraud are groundless and should not be a point of contention in the impeachment trial.

Yoon countered that he doubted the credibility of the election's fairness and sought understanding for declaring emergency martial law to confirm the facts, not to promote a conspiracy theory.

When a justice asked if he had ordered top military officers to remove lawmakers from the National Assembly, Yoon answered that he had not.

The session lasted about an hour and 40 minutes.

Hearings are expected to be held twice a week.

Yoon's lawyer said the president will attend every session unless there are special circumstances.