A ranking Seoul prosecutor was formally detained Monday pending trial on charges of receiving bribes worth hundreds of millions of won in return for favors, a special prosecution team looking into the case said.

The Seoul Central District Court approved the special investigation team's request to issue an arrest warrant for the disgraced prosecutor Kim Kwang-joon.

The 51-year-old prosecutor of the Seoul High Prosecutors' Office is accused of receiving a total of nearly 900 million won ($826,000) from Cho Hee-pal, the mastermind of South Korea's biggest-ever pyramid scheme, and the Eugene Group, a mid-sized conglomerate, in exchange for influence peddling.

Following Kim's arrest, Prosecutor-General Han Sang-dae issued a written apology.

"I, as the top prosecutor, feel deeply ashamed about a senior prosecutor's arrest on bribery charges. I offer my deepest apology to the people for causing a big disappointment and concern," Han said in the statement.

"The special prosecution team will conduct a thorough investigation into the case and bring the truth to light." Han plans to convene a meeting of senior prosecutors on Thursday to discuss prosecution reform measures, his aides said.

Kim also allegedly went on an overseas trip that was paid by an official of KTF Co., a mobile phone operator which is now absorbed into KT Corp.

The National Police Agency (NPA) initially launched a probe into Kim after securing circumstantial evidence that a man surnamed Kang, who is close to Cho, transferred 240 million won to a bank account suspected of being owned by Kim. Another 600 million won was also allegedly deposited into the account by the chief of an affiliate of the Eugene Group.

After the police investigation was made public, the prosecution immediately established its own investigation team to look into the allegations and filed for an arrest warrant for Kim on Thursday.

Kim is also suspected of taking between 80 and 90 million won from three other business groups, according to sources on the team.

The unprecedented dual investigation of a single corruption case has rekindled a long-running feud between police and the prosecution over their investigation rights. The two investigative authorities have been at odds for years over the scope of their power.

After prosecutors rejected the NPA's request for a court-issued warrant to search Kim's bank accounts on Friday, the NPA said it will postpone its decision to re-apply for the warrant.

The NPA, meanwhile, has found out some 7.8 billion won allegedly concealed in a bank account by Cho, officials said.

Cho was accused of swindling thousands of investors out of some 3.5 trillion won in the country's largest pyramid scheme. He fled to China amid a widening probe into his scam, and reportedly died last year.

As doubts surrounding his death still remain, however, police continue to pursue him. (Yonhap News)