Yoon is suspected of "insurrection," the news agency quoted Woo Jong-soo, head of the National Police Agency's Investigation Headquarters, who also told lawmakers that "the case has been assigned."
Moreover, South Korea's leading opposition Democratic Party (DP) has said that it will attempt to hold a vote on the impeachment motion against the president on December 7, the Yonhap news agency reported on Thursday.
Cho Seung-rae, the party's deputy spokesperson, said that it plans to hold a vote on Saturday at 19:00 local time (10:00 GMT) to allow the lawmakers of the ruling People Power Party to have enough time to discuss the motion.
Late on Tuesday, Yoon declared martial law "to purge pro-North Korean forces and maintain the liberal constitutional order." The president claimed that attempts by the South Korean opposition to impeach several high-ranking officials in his government posed a threat of political paralysis. The South Korean parliament voted to overturn the declaration of martial law. Of the 300 lawmakers, 190 were present, and the decision was made unanimously.
Under the constitution, the president is required to immediately revoke martial law once parliament votes against it by a majority. However, Yoon delayed issuing a formal statement for several hours. He explained that after the parliamentary decision, he had immediately ordered a government meeting to formalize the revocation, but a lack of quorum prevented the decision from being made. A subsequent meeting later officially repealed the martial law.
On Wednesday, Yonhap reported that six parties in South Korea, including the main opposition Democratic Party, had filed an impeachment bill against the president in the parliament, with a vote planned for December 6-7.