Former and present executives of the nation's leading financial institutions are to be summoned to the Diet this afternoon to testify about alleged ties with "sokaiya" corporate extortionists.

They are to testify as unsworn witnesses before the Upper House Budget Committee in connection with alleged irregularities involving sokaiya Ryuichi Koike. The executives are Setsuya Tabuchi, former chairman of Nomura Securities Co., and its former president, Hideo Sakamaki; and Kuniji Miyazaki, a former president of Dai-Ichi Kangyo Bank, and Katsuhiko Kondo, its president,

Koike is under arrest for allegedly receiving undue financial compensation from Nomura. DKB allegedly lent billions of yen to Koike, who reportedly used the funds to buy shares in Nomura and other securities firms.

The executive board of the Lower House Budget Committee decided May 27 to summon Yoshihisa Tabuchi, a former president of Nomura, and Kondo to testify as unsworn witnesses on June 5. The committee on June 6 will summon as unsworn witnesses Hideo Arato, a member of the Tokyo Metropolitan Assembly, in connection with a scandal involving the Orange Kyosai Kumiai mutual aid society, and Nobuharu Okamitsu, the former vice administrative minister of the Health and Welfare Ministry, in connection with allegations he took bribes from a social welfare facility operator.