Then South Korean presidential candidate Lee Jae-myung of the Democratic Party leaves after admitting defeat in the election at the party's headquarters in Seoul early on March 10, 2022. (PHOTO  / POOL / AFP)

SEOUL - South Korean prosecutors indicted opposition leader Lee Jae-myung on Wednesday on corruption charges in a $1 billion property development scandal dating to his previous stint as a mayor, the Yonhap news agency said.

Lee, chair of the main opposition Democratic Party, who lost to President Yoon Suk Yeol in last year's election, faces several charges, including bribery, corruption, breach of trust and conflicts of interests, Yonhap said.

Prosecutors have said Lee colluded with a group of private property developers when he was mayor of Seongnam, just south of Seoul, to help them rake in more than 800 billion won ($611.5 million) from the project, while inflicting losses of nearly 490 million won on the city

Prosecutors have sought to arrest him after an 18-month investigation into the 1.5 trillion won ($1.15 billion) construction project. Parliament, where Lee's party holds a majority, voted down a motion last month to waive immunity granted to lawmakers.

Prosecutors have said Lee colluded with a group of private property developers when he was mayor of Seongnam, just south of Seoul, to help them rake in more than 800 billion won ($611.5 million) from the project, while inflicting losses of nearly 490 million won on the city.

He was also accused of receiving or demanding more than 18 billion won from four companies in bribes to bankroll a financially strapped pro football club based in the city in return for administrative favors.

ALSO READ: S.Korea's Lee wins primary in presidential race amid scandal

Prosecutors also indicted Jeong Jin-sang, one of Lee's closest aides, who was arrested in November over the scandal, as his accomplice, Yonhap said.

Calls to the Seoul Central District Prosecutors' Office went unanswered.

Lee, who was Seongnam mayor from 2010-18, has denied any wrongdoing and accused prosecutors of fabricating charges out of political motives.

"The indictment was a predetermined outcome, but they just wanted to buy time for political shows," Lee told a meeting with senior party members. "Now that the ball is in the court, I will do my best to uncover the truth."

Lee's indictment is likely to deepen problems for the Democrats, who have faced criticism that the party abused its majority power to prevent his arrest even as more voters call for electing a new chief.

READ MORE: Free cash for all boosts rising S. Korea star to top of polls

In a poll by R&Search released on Wednesday, almost 48 percent of respondents said Lee should resign, and about 45 percent opposed. A Gallup survey last month showed about 57 percent supported eliminating lawmakers' immunity from arrest, while 27 percent said it is needed to fight political persecution.