Thousands of people rallied in a Tokyo park and marched to parliament to demand an end to nuclear power, ahead of the third anniversary of the Fukushima disaster.
Participants at Sunday's demonstration, one of several planned in cities across Japan, vowed to block a move by Prime Minister Shinzo Abe's government to restart some of the 48 idled reactors and renege on a pledge by the former government to reduce the nation's reliance on nuclear power.
This week marks the anniversary of the deadly earthquake and tsunami that hit the northern region on March 11, 2011. The Fukushima power plant suffered three meltdowns and still spews radiation into the atmosphere and sea.
Engineers say it will take at least four decades to dismantle the plant.