Chanting "Sayonara nuclear power" and waving banners, tens of thousands of people marched in central Tokyo on Monday to call on Japan's government to abandon atomic energy in the wake of the Fukushima nuclear accident.

The demonstration underscores how deeply a Japanese public long accustomed to nuclear power has been affected by the March 11 crisis, when a tsunami caused core meltdowns at three reactors at the Fukushima Dai-ichi complex.

The disaster _ the worst nuclear accident since Chernobyl _ saw radiation spewed across a wide part of northeastern Japan, forcing the evacuation of some 100,000 people who lived near the plant and raising fears of contamination in everything from fruit and vegetables to fish and water.

"Radiation is scary," said Nami Noji, a 43-year-old mother who came to the protest on this national holiday with her four children, ages 8-14. "There's a lot of uncertainty about the safety of food, and I want the future to be safe for my kids."

Police estimated the crowd at 20,000 people, while organizers said there were three times that many people.

In addition to fears of radiation, the Japanese public and corporate world have had to put up with electricity shortages amid the sweltering summer heat after more than 30 of Japan's 54 nuclear reactors were idled over the summer to undergo inspections.

Prime Minister Yoshihiko Noda, who took office earlier this month, has said Japan will restart reactors that clear safety checks. But he has also said the country should reduce its reliance on atomic energy over the long-term and explore alternative sources of energy. He has not spelled out any specific goals.

Before the disaster, this earthquake-prone country derived 30 percent of its electricity from nuclear power. Yet Japan is also a resource-poor nation, making it a difficult, time-consuming process for it to come up with viable alternative forms of energy.

Mari Joh, a 64-year-old woman who traveled from Hitachi city to collect signatures for a petition to shut down the Tokai Dai-ni nuclear plant not far from her home, acknowledged that shifting the country's energy sources could take 20 years.

"But if the government doesn't act decisively now to set a new course, we'll just continue with the status quo," she said Monday. "I want to use natural energy, like solar, wind and biomass."

Before the march, the protesters gathered in Meiji Park to hear speakers address the crowd, including one woman from Fukushima prefecture, Reiko Muto, who described herself as a "hibakusha," an emotionally laden term for survivors of the atomic bombs in Hiroshima and Nagasaki.

Those evacuated from around the plant remain uncertain about when, if ever, they will be able to return to their homes.

An AP-GfK poll showed that 55 percent of Japanese want to reduce the number of nuclear reactors in the country, while 35 percent would like to leave the number about the same. Four percent want an increase while 3 percent want to eliminate them entirely.

The poll, which surveyed 1,000 adults between July 29 and Aug. 10, had a margin of error of plus or minus 3.8 percentage points.

Author Kenzaburo Oe, who won the Nobel literature prize in 1994 and has campaigned for pacifist and anti-nuclear causes, also addressed the crowd. He and musician Ryuichi Sakamoto, who composed the score to the movie "The Last Emperor," were among the event's supporters.

(This version CORRECTS spelling of nuclear plant's name in second paragraph.)