Prosecutors have summoned opposition leader Lee Jae-myung to appear for questioning over suspicions surrounding a land development project in Seongnam, just south of Seoul, during his previous term as the city's mayor, according to legal sources Thursday.

The Seoul Central District Prosecutors Office is investigating allegations that Lee, the chairman of the main opposition Democratic Party, provided administrative favors to a private developer for the massive property project in Seongnam's Baekhyeon-dong district, during his term as the mayor in the mid-2010s.

Lee has been told to appear to face questioning as a suspect, the sources said, indicating the questioning is expected to take place late next week.

It would mark Lee's fourth appearance before the prosecution for questioning, following three rounds of summons over bribery charges surrounding corporate donations to the municipal football club Seongnam FC and corruption charges arising from another development project during his term as mayor.

The so-called Baekhyeon-dong scandal centers on allegations that the municipal government of Seongnam gave special treatment to the private developer, named Seongnam R&D PFV.

The company developed the former site of the Korea Food Research Institute in the district into apartment complexes between 2015 and 2016, and allegedly earned windfall profits worth 318.5 billion won ($289.7 million) after the city eased regulations requiring developers to set aside a portion of apartment units for less profitable rental homes.

Asia Developer, the largest shareholder in Seongnam R&D PFV, has reportedly earned a dividend income of about 70 billion won.

During the Baekhyeon-dong project, the city government changed its zoning regulations, and prosecutors suspect Lee was the final decision-maker who facilitated the change in the city's various approval processes to the advantage of the private developer. (Yonhap)