Japan sent three men to the gallows yesterday, ending a 20-month moratorium and effectively terminating a nascent debate on the country's controversial death penalty.

The Justice Minister, Toshio Ogawa, told the nation afterwards that Japanese law stipulates that he signs off on hangings and that the public strongly supports such executions. "I ordered these men's executions to fulfil my responsibility," he said.

The hangings were immediately condemned by Amnesty International and the head of the Japan Federation of Bar Associations, Kenji Utsunomiya. "Executions should be immediately suspended so that capital punishment can be debated nationally," he said.

Japan is one of the last developed countries to retain gallows. Opponents say the system, which keeps some prisoners in solitary confinement for years, is barbaric. But the latest government opinion polls put support for capital punishment at about 85 per cent.

Opponents hoped the left-leaning Democratic Party might scrap the gallows when it came to power in 2009. Instead, Keiko Chiba, the Justice Minister at the time, signed off on a pair of executions two years ago and ordered a panel to debate the issue. The panel recently wound up without reaching any conclusion.

Japan carried out no hangings in 2011 after journalists were allowed into the country's death chambers for the first time, sparking a low-key media debate that would probably now be "stifled", Mr Utsunomiya warned.

Criticism of the lack of transparency in the system has grown since Japan introduced a lay judge system three years ago, allowing ordinary people to examine serious criminal cases.

The men executed yesterday had been convicted of multiple murders. Yasuaki Uwabe, 48, a former transport worker, went on a rampage in a train station in southern Japan 13 years ago, killing five people and injuring 10.

Tomoyuki Furusawa, 46, broke into the home of his in-laws in 2002 in Yokohama, where his wife was sheltering from his abuse. He murdered her parents and 12-year-old son. Yasutoshi Matsuda, 44, robbed and murdered two women in rural Japan in 2001. Japan rarely executes single murderers.

Koichi Kikuta, a criminology professor and well-known opponent of the death penalty, said Mr Ogawa had not had enough time since becoming Justice Minister to examine the records of the men he executed. "It is arrogant of him to believe he has carried out his duty as Justice Minister," Mr Kikuta said.