So far this year, Japan has executed 13 people, all of them linked to the Aum Shinrikyo cult that launched the deadly sarin nerve gas attack in Tokyo in 1995.

It’s the highest number of people executed in Japan in a year since 2008, when 15 died by hanging. The US by comparison has put 14 people to death so far in 2018, according to the Washington DC-based Death Penalty Information Center.

Six more former members of the Aum cult were hanged today (July 26), following the executions earlier this month of seven others, including the cult’s founder Shoko Asahara, meaning all remaining Aum death row inmates have now been put to death.

In addition to the Tokyo attacks, which killed 13 people, the cult was also responsible for another such attack in Nagano in 1994 that killed eight, and the murders of a couple and their baby in 1989. The last remaining fugitive Aum member was arrested in 2012. All trials connected to the cult were officially completed in January this year.

Amnesty International, which campaigns for the abolishment of the death penalty worldwide, said that it was extremely rare for Japan to execute more than 10 people in a year, and to carry out two rounds of executions in a single month. The Mainichi newspaper reported that with the current emperor due to abdicate next year, authorities wanted to put an end to the cult for good before the end of the Heisei era, which began with the death of the previous emperor in 1989.

“This unprecedented execution spree… does not leave Japanese society any safer. The hangings fail to address why people were drawn to a charismatic guru with dangerous ideas,” said Hiroka Shoji, East Asia researcher at Amnesty.

Japan has also been criticized by bodies like the United Nations Committee against Torture for giving its inmates on death row exceptionally short notice for their execution, typically just hours before the hanging is to take place. However, a majority of people in Japan support capital punishment.

Aum Shinrikyo was founded in 1984 by Asahara. The cult’s followers believed that they would attain salvation after Doomsday if they followed Asahara, who as the “enlightened one” possessed the supreme truth.

Correction: The US has executed 14 people so far in 2018. An earlier version said the country had put 14 people on death row this year.