Seven members of the Aum Shinrikyo cult, which carried out the deadly 1995 sarin gas attack on the Tokyo subway, have been executed, Japanese officials said Friday.

Cult leader Shoko Asahara, whose real name is Chizuo Matsumoto, had been in prison for 22 years before his execution this week. The attack left more than a dozen people dead and thousands injured.

Twelve other members of Aum Shinrikyo were sentenced to death for their roles in the Tokyo attack. Asahara's death sentence was finalized in 2006, according to public broadcaster NHK, but trials of his co-conspirators dragged on for a further 12 years.

Since those proceedings finished earlier this year, the days of the Aum Shinrikyo members had been numbered, even as opponents of the death penalty attempted to block the executions.

Asahara was one of seven members of the cult hanged this week. The others are Tomomasa Nakagawa, Tomomitsu Niimi, Kiyohide Hayakawa, Yoshihiro Inoue, Seiichi Endo and Masami Tsuchiya, according to Japanese Justice Minister Yoko Kawakami.

Six other people are still sentenced to die in connection to the 1995 attack and other Aum Shinrikyo crimes. The date of their executions is not known.

Executions in Japan are done in secret, with no advance warning given to the prisoner, their family or legal representatives, according to Amnesty International. Prisoners often only learn hours before that they are to be killed.

Shizue Takahashi, a victims group representative and widow of a Toyko Metro employee who died in the sarin attack, told reporters she was "surprised" by the sudden execution.

"When I think of those who died because of them, it was a pity (my husband's) parents and my parents could not hear the news of this execution," she said. "I wanted (cult members) to confess more about the incident, so it's a pity that we cannot hear their account anymore."

In a statement Friday, Amnesty said the execution of Asahara and other Aum Shinrikyo members would not deliver justice for the Tokyo attack.

"The attacks carried out by Aum were despicable and those responsible deserve to be punished. However, the death penalty is never the answer," said Hiroka Shoji, East Asia researcher at Amnesty International.

"Justice demands accountability but also respect for everyone's human rights. The death penalty can never deliver this as it is the ultimate denial of human rights." (CNN)

•Photo shows a gate of a Tokyo detention center on July 6, 2018, where Shoko Asahara, whose real name is Chizuo Matsumoto, was hanged for masterminding the 1995 sarin gas attack on the Tokyo subway system.

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