Japan this morning hanged three death-row inmates in its first executions since 2010, reigniting the debate over capital punishment in one of the world's richest countries.

"Today, three executions were carried out," Justice Minister Toshio Ogawa told reporters. "I have carried out my duty as a justice minister as stipulated by law," he said.

The hangings, of three people convicted of multiple murder, are only the second time the left-leaning Democratic Party of Japan has implemented the death penalty since it came to power in September 2009.

Japan did not execute anyone in 2011, the first year in nearly two decades the country has not carried out a single death sentence amid a debate on the rights and wrongs of capital punishment.

Ogawa said following the executions that 132 people remained on death row.

These are known to include Shoko Asahara, the mastermind behind the 1995 sarin gas attacks on the Tokyo subway.

The last execution in Japan was in July 2010 when then justice minister Keiko Chiba, a former socialist and lawyer, approved the hanging of two inmates, despite her long-time opposition to the death penalty.

The two were Kazuo Shinozawa, 59, who killed six people by setting fire to a jewellery store, and Hidenori Ogata, 33, who killed a man and a woman and seriously injured two others.

The death penalty in Japan is usually reserved for multiple homicides.

In an unusual move, Chiba attended the executions and later allowed the media to visit the execution chamber at the Tokyo Detention House in a bid to increase public debate over the death penalty.

Apart from the United States, Japan is the only major industrialised democracy to carry out capital punishment, a practice that has earned Tokyo repeat protests from European governments and human rights groups.

In a legal quirk, executions -- always carried out by hanging in Japan -- are banned over the New Year period, with a moratorium between December 29 and January 3 as well as on weekends and public holidays.