Tokyo (CNN) -- Tens of thousands of people crowded into a park in central Tokyo on Monday to protest the use of nuclear power in Japan, highlighting the growing opposition to atomic energy in the country since the crisis at the Fukushima Daiichi power plant.
The peaceful demonstration took place on Japan's national day in an area the size of a large sports field in Yoyogi Park, near the bustling shopping and nightlife district of Shibuya.
The event attracted so many people on a hot July public holiday that many spilled out into the surrounding streets, unable to enter the main area. It brought together a broad mix of Japanese people, from seasoned environmental activists to families who hadn't participated in a protest before.
The colorful flags dotting the crowd along with the warm weather gave the demonstration the appearance of a summer music festival, but its message was deeply serious.
The prominent musician and composed Ryuichi Sakamoto addressed the demonstrators from a stage, calling for an end to nuclear power in Japan. Participants held banners echoing his statements and criticizing the government.
Protesters then marched around the surrounding streets, chanting anti-nuclear slogans and drawing traffic to a halt.
Demonstrations against atomic energy have become a regular part of Japanese public life since the devastating earthquake and tsunami in March 2011 set off the nuclear disaster at the Fukushima plant. And the protests appear to be gaining momentum.
Each Friday, anti-nuclear demonstrators gather outside the Japanese prime minister's office. That protest has been getting bigger and bigger every week, especially since the Japanese government announced the reactivation of the first nuclear reactor since the Fukushima crisis.
Though no deaths have been attributed to the nuclear accident, the earthquake and tsunami killed more than 15,000 people in northeastern Japan. The damaged Fukushima spewed radiation, prompting the government to evacuate tens of thousands of people.
A recent report by an independent panel commissioned by the Japanese parliament said the Fukushima crisis was a "man-made disaster" that could have been avoided. It criticized the actions of the government, regulators and the plant's operator, Tokyo Electric Power Co.
CNN's Junko Ogura reported from Tokyo; Jethro Mullen from Hong Kong.