TOKYO — Beating drums and waving flowers, protesters in Tokyo and other major cities rallied against the use of nuclear power on Saturday, three months after a devastating tsunami set off a nuclear crisis.

Anger over the government’s handling of the accident at the Fukushima nuclear plant has erupted in recent weeks after revelations that the damage at the plant, and the release of radioactive material, was far worse than previously thought. Mothers worried for their children’s health, as well as farmers and fishermen angry about their damaged livelihoods, have been especially critical of the government of Prime Minister Naoto Kan.

The disaster has also prompted a national debate about Japan’s heavy reliance on nuclear power despite the country’s history of devastating earthquakes and a deep public distrust of the nuclear industry. In perhaps his sole move that has won popular support, Mr. Kan ordered the shutdown of a separate nuclear power plant in central Japan until it can bolster its tsunami defenses. But recent politicking in a gridlocked Parliament has added to the public’s disenchantment.

“We now know the dangers of relying on nuclear power, and it’s time to make a change,” Hajime Matsumoto, one of the rally’s organizers, told a crowd in a central Tokyo square that eventually grew to about 20,000 people, according to organizers’ estimates.