Scores of Aum members have faced trial over the attack - 13 were sentenced to death, including Asahara.
The police and the Public Security Intelligence Agency are gathering intelligence and closely monitoring followers who could possibly attempt to retrieve the bodies of Asahara and the six others.
Asahara, who had suffered partial blindness since childhood, was detained in May 1995, two months after the nerve agent attack on March 20, 1995, which killed 13 people and injured more than 6,000.
Yuji Ogawara, who heads a lawyers' group against the death penalty at the Japan Federation of Bar Associations, said the executions do not bring closure to Aum's crimes.
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With their deaths, Japan will now have to grapple with the aftermath of unanswered questions over the crimes - with no longer any chance of hearing explanations directly from Asahara or the six others.
They were criticized by rights group Amnesty International, which described the cult's acts as "despicable" but said "the death penalty is never the answer".
Police leave an Aum Shinrikyo compound in the small village of Kamikuishiki at the foot of Mount Fuji on March 28, 1995.
AUM Shinrikyo renamed itself Aleph in January 2000.
She said the crime affected not only Japan but also sowed fear overseas.
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The horrifying scenes in the aftermath of the attack shocked a country where the crime rate is relatively low and people tend to take their personal safety for granted.
At a press conference Friday, former Aum Shinrikyo spokesman Fumihiro Joyu said he carried a "heavy shared responsibility" for the group's crimes. The attack claimed the lives of thirteen people, over 6,300 people were injured. All told, 19 cult members, including Asahara, were apprehended and tried for their crimes. At its peak, Asahara had tens of thousands of followers worldwide. After all, the upper echelons of Aum Shinrikyo being held on death row had denied being directly involved in the terrorist attack.
Aum Shinrikyo's killings began in November 1989, when lawyer Tsutsumi Sakamoto - who was working on a class action case against the cult - was brutally murdered along with his wife and child.
Major Japanese media are reporting that some disciples of doomsday cult leader Shoko Asahara have also been executed.
"I've been in pain for years". Despite this, over 2,000 members of another offshoot cult still follow the teachings of Shoko Asahara.
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At its peak, the group had 10,000 members in Japan and 30,000 followers in Russian Federation, the Associated Press reports.