SEOUL - South Korea's constitutional court on Thursday held the second hearing for the impeachment trial of President Yoon Suk-yeol, who was arrested the previous day over his martial law imposition.

During the second formal hearing, the court justices adopted evidence and witnesses and dismissed Yoon's defense counsel's claim that the evidence and witnesses were illegal.

Next hearings will be held on 21 and 23 of January and on 4, 6, 11 and 13 of February.

Two newly appointed justices filled two of three vacancies in the nine-member bench, performing their duties earlier this month.

To oust Yoon from office, at least six justices of the court are required to uphold the impeachment.

Yoon was arrested in the presidential residence Wednesday, becoming the country's first sitting president to be arrested.

After being questioned at the anti-corruption agency's office in Gwacheon, just south of Seoul, Yoon was taken into custody at the Seoul Detention Center in Uiwang, just 5 km away from the office.

The impeachment motion against Yoon was passed in 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, who was named by investigative agencies as a suspected ringleader on an insurrection charge, declared a martial law on the night of Dec. 3, but it was revoked by the National Assembly hours later.