OSAKA -- Fresh arrest warrants were served Sunday for the head of the Kinki Postal Administration Office and the postmaster at Kyoto Chuo Post Office in connection with a vote-soliciting scandal involving more than a dozen senior postal officials.

According to investigators with the Osaka Prefectural Police, the new warrants were served on Tsuyoshi Mishima, 59, head of the Kinki Postal Administration Office, and Hiromasa Akai, 59, who heads the Kyoto Chuo Post Office.

The two are suspected of having illegally wielded their influence to urge postmasters to support Kenji Koso, a Liberal Democratic Party candidate who succeeded in winning a seat in the July House of Councilors election, during a gathering of postmasters in northern Osaka prefecture in early February.

The two suspects have already been arrested after similar allegations were made about a separate postmasters' meeting held in March. They have admitted to the latest allegations, police said.

The latest development is expected to put even more pressure on Koso, who has brushed aside calls to resign, when the extraordinary Diet session begins Sept. 27.

Koso headed the Kinki Postal Administration Office between June 1998 and July 1999. He could be stripped of his Diet seat if convicted, because election laws stipulate that if a former government official runs in a national election held within three years of his resignation, any election violations committed by his successor at the candidate's request invalidate the election.