South Korean prosecutors have opened an investigation into President Yoon Suk Yeol, his interior minister, and the now-former defence minister over their roles in an attempt to impose martial law, Yonhap news agency reported on Thursday.
Kim Yong-hyun, who resigned as South Korean defence minister over his involvement in Tuesday's martial law order, also faces a travel ban as prosecutors investigate, Yonhap said. The other two do not face such bans.
Citing unspecified threats from "anti-state forces" and obstructionist political opponents, Yoon imposed martial law for about six hours before reversing course after parliament voted to oppose the move.
Yoon now faces an impeachment vote on Saturday.

European leaders rally behind Greenland in face of renewed US threat
Maduro opponent Machado vows to return to Venezuela, wants election
Ukraine security guarantees to include binding commitments: draft Paris summit
Nicolas Maduro pleads not guilty to charges of narco-terrorism
Flash floods in Indonesia's North Sulawesi kill 14
Swiss bar in deadly blaze had missed six years of safety checks
Nestle recalls infant formula batches across Europe on food safety concerns
UN chief Guterres raises concerns about instability in Venezuela
