Lee was questioned for about three hours at an unidentified location in Seoul over claims that he was involved in a 2001 stock manipulation case, Yonhap news agency said.
Lee "answered (questions) in detail in a sincere manner," Kim Hak-geun, an official at the special prosecutor's office in Seoul, told reporters according to the report.
Officials at Lee's offices and the special prosecutor's office could not immediately be reached for comment on the report.
The unprecedented investigation of a president-elect was prompted by accusations — made by Lee's liberal rivals — that Lee was directly involved with an investment firm at the center of an alleged stock manipulation case.
Lee, a former chief executive officer of Hyundai Engineering and Construction, has flatly denied the allegations and has pledged to abandon the presidency if he is found to have been involved.
In December, state prosecutors cleared Lee of wrongdoing while indicting his Korean-American former business partner, who was extradited from the U.S. for allegedly spreading false information to boost stock prices and for fleeing with millions of dollars in ill-gotten gains.
Liberals in South Korea's parliament, however, accused the prosecution of bias and passed a bill two days before December's presidential vote calling for an independent counsel investigation. They also released a 2000 video showing Lee bragging in a speech that he founded the firm involved. Lee said the comments were taken out of context.
Under the bill approved by outgoing President Roh Moo-hyun, the special prosecutor has until Feb. 23 to investigate the case — a deadline that falls two days before Lee's inauguration.
It is widely believed that the probe will not lead to any punishment for Lee because the constitution grants sitting presidents immunity from criminal lawsuits, unless they are accused of serious crimes such as treason.
Güncelleme Tarihi: 18 Şubat 2008, 11:58