Prosecutors investigating alleged bribery ahead of the 2021 main opposition Democratic Party(DP) leadership election raided the residence of former DP chief Song Young-gil and other locations.

The Seoul Central District Prosecutors' Office on Wednesday began the search at Song's home in Seoul's Yongsan District as well as the home of a former DP policy committee member surnamed Kim in its probe into bribery and violations of the political fund law.

Prosecutors suspect that a sponsor group outside the opposition party served as a conduit for illegal political donations for Song's campaign ahead of the 2021 convention that ultimately resulted in his election as party chief.

The state agency reportedly detected signs of a legislation lobby involving a DP policy committee member while tracking down the sponsor group's finances.

Such suspicions arose during the prosecution's probe into alleged distribution of 94 million won, or around 70-thousand U.S. dollars, in bribes to DP lawmakers and members by DP-turned-independent Reps. Youn Kwan-suk, Lee Sung-man and others to secure Song's victory.

The state agency plans to summon Song and Kim for questioning after scrutinizing the collected evidence.