Former South Korean president Lee Myung-bak reported to prosecutors for questioning in a corruption probe Wednesday and apologised for the controversy.
"I'm very sorry for causing concern to the people," Lee said on arrival at the prosecutors' office in Seoul.
The investigation into Lee means all living former South Korean presidents have been convicted, charged, or embroiled in criminal inquiries.
Allegations of corruption involving the 76-year-old's relatives and aides during his 2008-2013 presidential term have mounted in recent weeks as prosecutors investigate multiple cases of bribery amounting to millions of dollars.
Two of the ex-president's former aides have been arrested and the homes and offices of his brothers raided.
South Korean presidents have a tendency to end up in prison -- or meet untimely ends -- after their time in power, usually once their political rivals have moved into the presidential Blue House.
Lee's successor Park Geun-hye was ousted last year over a massive corruption scandal that emerged in 2016.
The verdict in her trial on charges of bribery and abuse of power is due next month, with prosecutors demanding 30 years in jail.
Lee's own predecessor, the liberal Roh Moo-hyun, committed suicide by jumping off a cliff after being questioned over corruption allegations in 2009.
© 2018 AFP