An anti-nuclear power rally Sunday near the Diet building drew 60,000 people, according to the three groups that organized the event, including one led by Nobel literature laureate Kenzaburo Oe.
The Metropolitan Police Department, which provided security for the event, estimated the number of participants at 20,000 to 30,000.
The protesters marched to the Diet after staging rallies in a park and a site near the Diet building earlier in the day.
"Resuming (operating) nuclear power plants is a betrayal to Fukushima," Oe said at the rally in Shiba Park in Minato Ward.
He also said public opinion is strongly in favor of scrapping all of Japan's nuclear power plants.
The protest was organized by the Metropolitan Coalition Against Nukes, which has been holding weekly rallies outside the prime minister's office since the start of the Fukushima nuclear crisis in 2011, and a group of labor unions nationwide.
Also taking part was the group led by Oe and other celebrities that has organized an ongoing anti-nuclear campaign dubbed "10 Million People's Action to say Goodbye to Nuclear Power Plants."