South Korea's Prime Minister Lee Wan-koo delivers his speech during his departure ceremony at a government complex in Seoul, South Korea, April 27, 2015. [Photo/Agencies]

SEOUL - Former South Korean Prime Minister Lee Wan-koo was summoned by the prosecution Thursday for questioning on suspicions that he was involved in a bribery scandal two years ago.

Lee, who resigned as the country's second-highest administrative post on April 27, appeared at 10 am local time ( 0100 GMT) in the Seoul High Prosecutor's Office.

He has been suspected of receiving 30 million won ($28,000) in bribes during the by-election campaign period in April 2013 from a businessman who killed himself on April 9.

Sung Wan-jong, the former ruling party lawmaker and businessman who ran the now-bankrupt construction firm, left a brief memo that listed eight heavyweight politicians, including Lee and current presidential chief of staff Lee Byeong-kee, alongside currency figures.

Lee had strongly denied his involvement, saying that he did have few acquaintances with Sung. Lee even said that he would kill himself if any evidence comes out for conviction.

The former prime minister, however, stepped down as it turned out that Lee had made some 200 phone calls with Sung in the past year while having had dozens of meetings with Sung.

Lee, who had taken office in February, became the country's shortest-servicing prime minister in history.