Opposition leaders demanded on Sunday a full accounting of the money management scandal surrounding Democratic Party of Japan Secretary General Ichiro Ozawa.
"It's quite alarming that the aides were nabbed one after the other," Liberal Democratic Party President Sadakazu Tanigaki said of the arrests of Ozawa's former and current aides.
New Komeito chief Natsuo Yamaguchi also chimed, addressing the issue on a TV talk show.
"It's now in question how a lawmaker will explain the treasurers' mismanagement," he said.
Japanese Communist Party leader Kazuo Shii said lawmakers must try to get the whole truth about the scandal during the upcoming Diet session.
Prosecutors have arrested two former Ozawa secretaries, including DPJ lawmaker Tomohiro Ishikawa, for allegedly falsifying political funding reports in connection with a land purchase made by Ozawa's fund management body in 2004.
Among DPJ lawmakers, Kozo Watanabe, a former Lower House vice speaker, said on TV that Ozawa "is morally responsible because he faces the allegations. I'm keeping a close watch on how he will explain them."
Deputy Prime Minister Naoto Kan said he is concerned that "investigative information has been one-sidedly leaked to the media," but declined to comment on the allegations.
Ozawa, meanwhile, apologized to his party at a local DPJ meeting in the city of Nagasaki on Sunday.
"I feel sorry that I have caused worry again," he said.