Shoko Asahara, the leader of the Aum Shinrikyo cult that carried out a deadly sarin attack on Tokyo's subway in 1995, was executed on Friday, local media reported.
The justice ministry would not immediately confirm the reports. He had been on death row for over a decade for the attack that killed 13 people and injured thousands more.
His hanging Friday was the first execution of any of the 13 cult members on death row for the attack and other crimes.
The March 20, 1995 incident shocked the world and prompted a massive crackdown.
It paralysed the Japanese capital, turning it into a virtual warzone as injured people staggered out of the underground struggling for breath with watering eyes.
Some keeled over, foaming at the mouth, with blood streaming from their noses, as the rushhour attack unfolded.
Asahara was born Chizuo Matsumoto in 1955 on the southwestern island of Kyushu and changed his name in the 1980s, when the Aum cult was being developed.
Virtually blind, he was seen as a charismatic speaker who cloaked himself in mysticism to draw recruits to the doomsday cult he developed in the 1980s.
The Aum cult, now renamed Aleph, officially disowned Asahara in 2000, but it was never banned.
Experts says the former guru retained a strong influence, with some members using pictures of him and recordings of his voice for meditation.