President Yoon Suk Yeol gives a public statement at the presidential office, in this photo provided by Yoon's office, in Yongsan District, Seoul, Dec. 12. Yonhap

The anti-corruption investigation body on Thursday summoned President Yoon Suk Yeol to appear for questioning this weekend over his brief imposition of martial law.

The Corruption Investigation Office for High-ranking Officials (CIO) issued the summons ordering Yoon to appear at its office in Gwacheon, just south of Seoul, at 10 a.m. Sunday.

This marked the CIO's third summons after Yoon ignored two previous summonses, including one for questioning on Christmas Day.

The CIO has teamed up with the police and the defense ministry's investigation unit to look into allegations Yoon incited an insurrection and abused his power when he declared martial law on Dec. 3.

Three summonses is typically the maximum before investigative agencies seek an arrest warrant against a suspect.

The CIO reportedly considered seeking a warrant after Yoon snubbed its second order but opted to issue a third summons in order to eliminate any doubts about procedural flaws.

Yoon has yet to submit a notice of attorney appointment to the investigation team.

A lawyer involved in the formation of his legal defense team earlier said the president prioritizes his impeachment trial over the investigation. (Yonhap)