Prosecutors on Thursday searched the office of a ruling party lawmaker amid allegations that the politician paid money to local assembly members in return for supporting a candidate he backed in a Tokyo ward mayoral election.

Several assembly members of Koto Ward have been already questioned on a voluntary basis about the suspected payments by House of Representatives lawmaker Mito Kakizawa that may constitute vote-buying, investigative sources said.

Kakizawa, a member of the Liberal Democratic Party, resigned as senior vice justice minister late last month for having proposed to former Koto Mayor Yayoi Kimura that she use an online advertisement during her campaign, an alleged violation of the election law.