Twelve people were killed and 5,500 injured when sarin nerve gas was released in the city's subway system.
Families of victims were joined by former and current subway employees among others marking the attack, the Kyodo News Agency reports. Sixteen workers at the Kasumigaseki Station stood in silence for 30 seconds at 8 a.m.
The wife of a slain employee placed flowers at the station next to a flower shrine.
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