Thousands of people are expected to form a "human chain" around Japan's parliament on Sunday to demonstrate against the use of nuclear power following last year's atomic crisis at Fukushima.
It will be the latest in a string of protests in Japan, which has seen a rising tide of anti-nuclear sentiment since Prime Minister Yoshihiko Noda in June ordered the restart of two reactors.
Noda defended the move citing looming power shortages after Japan switched off its 50 nuclear reactors -- which provided the resource-poor country with a third of its energy -- in the wake of the Fukushima disaster.
Weekly demonstrations outside the prime minister's residence have drawn tens of thousands of people and a rally in west Tokyo earlier this month saw a crowd that organisers claimed was about 170,000-strong.
The Sunday demonstrations, scheduled to start about 3:30 pm (0630 GMT), will see a march through the capital before protesters form a human chain around the legislature in the evening to demand a "swift abolition of nuclear power".
Early Sunday a dozen police vehicles were stationed on the street facing the prime minister's residence and the parliament.
Hiroshi Sakurai, a 65-year-old painter, said he arrived on the street to join the anti-nuclear rally for the first time.
"After the Fukushima disaster, I came to feel strongly that it is human arrogance to think that we can control nuclear power with our technology," he told AFP.
Protest organiser Kaori Echigo said demonstrators from across the nation of 127 million people were expected to descend on Tokyo for the march.
"Not only people from Tokyo but also people from Hokkaido (in the north), Nagano (in central Japan) and Osaka are expected to come by bus," Echigo told AFP.
The latest rally comes less than a week after a damning government-backed report on last year's crisis said Japanese officials and Tokyo Electric Power (TEPCO), operator of the crippled Fukushima plant, ignored the risk of an atomic accident because they believed in the "myth of nuclear safety".
A separate parliamentary report said the worst nuclear accident in a generation was a man-made disaster, marked by a lack of oversight and collusion between TEPCO, the government and regulators.
The giant utility largely cleared itself of blame, saying the size of last year's earthquake and tsunami was beyond all expectations and could not have reasonably been foreseen.
A 9.0-magnitude earthquake and tsunami on March 11, 2011, crippled cooling equipment at the Fukushima Daiichi plant, triggering meltdowns that spewed radioactivity and forced tens of thousands of residents to flee.
The rising anti-nuclear sentiment in Japan has also led to the launch of Greens Japan, a political organisation aiming to field candidates with an environmental agenda in parliamentary elections.
"A party that strongly pursues environmental policies is needed," Akira Miyabe, the group's 59-year-old deputy head, is quoted by Kyodo News as saying at an inaugural meeting on Saturday.