Tokyo Metro Co. employees observed a minute of silence at 8 a.m. local time, around the same time that the attacks occurred, Kyodo News reported.
On March 20, 1995, members of the Aum Shinrikyo cult, now known as Aleph, released the nerve gas at five stations on three central Tokyo subway lines, killing 13 people and making more than 6,000 others ill.
''There are still victims who are bedridden and under treatment. Please do not forget about us,'' said Shizue Takahashi, the 64-year-old widow of a worker at Kasumigaseki Station killed in the attacks.
Earlier this month, Masumi Tsuchiya, 46, became the 11th Aum member to be sentenced to death.
Chizuo Matsumoto, founder of the cult more commonly known as Shoko Asahara, has been on death row for overseeing a succession of crimes including the sarin gas attacks, the newspaper said.