Democratic Party of Korea leader Lee Jae-myung on Saturday appeared at a district prosecutors' office in Seoul. (Yonhap)

South Korea's main opposition party leader Lee Jae-myung called the Yoon Suk Yeol administration a “dictatorial regime” controlled by prosecutors as he appeared at a district prosecutors' office in Seoul on Saturday as a suspect to a high-profile land corruption scandal.

Lee, defeated by former prosecutor Yoon in the 2022 presidential election in a narrow margin, has since been facing a number of corruption allegations that were raised even before he became a candidate. Appearing before prosecutors on Saturday morning, he submitted a 33-page written statement, which indicated that he would refuse to answer any other questions during interrogations. The interrogation lasted for over 12 hours.

Earlier in January, he appeared for questioning for a separate bribery allegation.

"This is the moment when the rule of the law is ignored and constitutional order is disrupted by the dictatorial regime of Yoon and prosecutors," Lee said as he was entering the Seoul Central District Prosecutors' Office for questioning at 10:23 a.m. "This is the worst scene, in which the dictatorial regime privatizes the state authority in order to eliminate a political opponent."

Prosecutors are looking into alleged acts of corruption by Lee in the controversial land development during his time as mayor of Seongnam, Gyeonggi Province, in the mid-2010s. Lee is suspected to have arranged private gains of at least 42.8 billion won ($34.7 million) to go to his associates in return for approving the controversial plan.

Democratic Party of Korea leader Lee Jae-myung on Saturday waves his hand to supporters before he entered a district prosecutors' office in Seoul. (Yonhap)

The case concerns a state-sponsored land redevelopment plan to build a residential complex in Daejang-dong in southwestern Seongnam.

The city-approved plan had allowed an inexperienced asset management company, Hwacheon Daeyu, to take larger total dividends than a public-sector company, even though Hwacheon Daeyu and its related parties held only a combined 7 percent stake in the consortium, while the public-sector Seongnam Development Corp. had a 50 percent stake.

Other figures from Hwacheon Daeyu and Seongnam Development have been indicted on charges of colluding to conceal the profits from the project and distribute them disproportionately to Hwacheon Daeyu. The prosecution views the arrangement as the breach of trust, which in Korea is punishable by at least five years in prison in cases where the profits exceed 5 billion won.

Prosecutors are looking into the identities of related parties who remain unknown and received a considerable amount of profit.

A court trial heard Friday that one of the related parties could be associated with Lee, as an official of Seongnam Development said in a testimony that the gains were to be used for campaign funding for Lee's presidential race. Another court trial in October indicated that Lee was the top decisionmaker that approved the consortium's dividend payment structure.

The nation's prosecution service has been investigating the matter for the past 16 months.

The land development-related corruption probe is one of several investigations into Lee. He also faces allegations that Lee solicited contributions of companies to a soccer club in exchange for their land use approval during his tenure as the Seongnam mayor. Also, Lee is also alleged to have helped companies acquire business rights in North Korea when he was governor of Gyeonggi Province from 2018 to 2021.

Lee leads the Democratic Party of Korea, which controls the majority of seats in the National Assembly.