SEOUL -- South Korea's constitutional court on Thursday designated one more hearing of President Yoon Suk-yeol's impeachment trial.

The court said the ninth hearing will be held at 2:00 pm local time (0500 GMT) on Feb 18.

The eighth formal hearing was held earlier on Thursday with the arrested president being present.

Yoon, dressed in suit and red necktie as before, presented himself at the courtroom in central Seoul at around 10:00 am local time (0100 GMT). He had attended the hearings except the first and second ones.

Col. Cho Sung-hyun of the Capital Defense Command testified in the hearing that the arrested former commander ordered him to break into the National Assembly's main building and drag out lawmakers who gathered to lift the martial law.

Yoon declared an emergency martial law on the night of Dec 3 last year, but it was repealed by the opposition-led parliament hours later.

It is illegal and unconstitutional to block the National Assembly, a sole body with the right to revoke martial law.

Cho Tae-yong, chief of the National Intelligence Service (NIS), acknowledged in the hearing that he exchanged text messages with Yoon's wife, Kim Keon-hee, around the time of martial law declaration.

It indicated Kim's possible involvement in the martial law imposition and follow-up measures.

The motion to impeach Yoon was passed through the National Assembly on Dec 14 last year and was delivered to the constitutional court to deliberate it for up to 180 days, during which Yoon's presidential power is suspended.

Yoon was apprehended in the presidential office on Jan 15, becoming the country's first sitting president to be arrested.

Yoon, who was named as a suspected ringleader of insurrection, was indicted under detention on Jan 26, becoming the country's first incumbent president to be put on trial in custody.