Four death-row inmates were hanged April 10, bringing to 10 the number of executions Justice Minister Kunio Hatoyama has approved since he took office last August.

Hatoyama released the names and details of the inmates — in line with the new disclosure policy he earlier introduced — at a hastily arranged news conference.

"I must issue a very sad notice," he told media before revealing that Masato Sakamoto, 41, and Kaoru Akinaga, 61, went to the gallows at the Tokyo Detention House while Katsuyoshi Nakamoto, 64, and Masaharu Nakamura, 61, were executed at the Osaka Detention House.

Hatoyama in December approved three hangings and three more in February.

His third round of executions cut the number of death-row inmates to 104 while putting him even with his predecessor, Jinen Nagase, who approved 10 executions during an 11-month stint in office.

Hatoyama explained that the April 10 hangings "brought down the number of death-row inmates to the level it was when I became justice minister," but later clarified that this figure does not play a role in his judgment when approving executions.

Although Hatoyama said at the news conference that he approved the executions after "careful and thorough examination of each case," human rights groups and lawyers denounced the multiple hangings.

Pointing out there have been four cases in which a death-row inmate was pronounced innocent in retrials, the Japan Federation of Bar Associations demanded the government halt executions until improvements are made in the justice system.