"No to nuclear bombs! No more Fukushima!" chanted the protesters, some of them with little children, to the sounds of rock music and raggy performed by musicians in bright clothes.

"I learnt about the demonstration through Twitter, said a 43-year-old protester who had brought his children aged two and six. "I want to do everything possible to stop nuclear power industry, not for our sake but for the sake of our children."

The powerful quake and a tsunami hit northeastern Japan on March 11 causing nearly 15,000 deaths and disabling the cooling systems at Fukushima reactors. Radioactive elements were later found in the water, air and food products in some parts of Japan.

Early this week TEPCO, the operator of the nuclear plant, began dumping 11,500 of low-level radioactive water into the Pacific to empty reservoirs needed for high-level radioactive water. The company said it regretted the decision but this was the only option.