SEOUL (AFP) - Former South Korean prime minister Lee Wan Koo was questioned by prosecutors on Thursday as part of a widening corruption probe that prompted his resignation last month.

"Nothing can beat the truth," Mr Lee told reporters as he turned up at the main prosecutors' office in Seoul in response to a summons. "I will tell my side of the story in detail to prosecutors... and hope that this all will be resolved."

Mr Lee stepped down as prime minister after being accused of taking 30 million won (S$36,300) in bribes.

The accusation was made by businessman Sung Wan Jong, who later committed suicide. In an apparent suicide note, Sung listed the names of other officials, including current and former senior aides to President Park Geun Hye, suggesting he had also given them money.

All those implicated, including Mr Lee, have denied the allegations.

Bribery scandals involving politicians and rich businessmen have been a fixture of South Korean politics for decades.

Two former presidents served prison terms for taking bribes and dozens of heads of major business groups have been convicted of forming slush funds to lobby politicians.

After accepting Mr Lee's resignation as prime minister, Ms Park vowed reforms to "root out prevalent, deep-rooted corruption".