Thousands of people formed "a human chain" around Japan's parliament complex Sunday to demand the government abandon nuclear power -- the latest in a series of peaceful demonstrations on a scale not seen in the nation for decades.

Also Sunday, voters went to the polls in a closely watched election for governor of southwestern Yamaguchi prefecture, where an outspoken anti-nuclear candidate was running. Japanese media reported his loss late Sunday, citing exit polls, although official results had not been tallied.

Protesters said they were angry the government restarted two reactors earlier this month despite safety worries after the multiple meltdowns at the Fukushima Dai-ichi nuclear plant in March last year. The reactors were the first to return to operation since May, when the last of Japan's 50 working reactors went offline for routine checks.

Banging on drums and waving balloons and banners, protesters marched from a Tokyo park and lined up along the streets around the parliament building chanting, "Saikado hantai," or "No to restarts," and later lit candles.

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"All these people have gotten together and are raising their voices," said Shoji Kitano, 64, a retired math teacher who was wearing a sign that read, "No to Nukes."

Kitano said he had not seen such massive demonstrations since the 1960s. He stressed that ordinary Japanese usually don't demonstrate, but were outraged over the restarting of nuclear power.

Similar demonstrations have been held outside the prime minister's residence every Friday evening. The crowds have not dwindled, as people get the word out through Twitter and other online networking. A July 16 holiday rally at a Tokyo park, featuring a rock star and a Nobel laureate, drew nearly 200,000 people.

The crowd appeared to be smaller Sunday. Kyodo News service estimated it at about 10,000 people. Participants said they came from across Japan, underlining the widespread appeal of the protests.

Prime Minister Yoshihiko Noda defended his decision to restart the two reactors at Ohi nuclear plant in central Japan as necessary to maintain people's living standards. Other reactors are also expected to go back online, one by one.

Reports from government and legislative investigations of the Fukushima disaster have done little to allay people's fears. A recent probe blamed a "Japanese mind-set" which it said had allowed collusion between the plant's operator and regulators.

Adding to protesters' frustrations is the support nuclear power has received from regional governments where the plants are located. They said they planned to vote anti-nuclear candidates into office to effect change.

Typically, relatively poor rural and fishing areas, far from Tokyo, have been chosen for construction of nuclear plants, with residents won over with jobs and subsidies. There is a plan to build a nuclear plant in Yamaguchi prefecture, but doubts are growing over whether that can be carried out.

Tetsunari Iida, a candidate in Sunday's Yamaguchi gubernatorial election, opposes that plan and nuclear power in general. Kyodo and other Japanese media said Iida was defeated by old-guard candidate Shigetaro Yamamoto, a former bureaucrat who is more conciliatory toward the government's energy policy.

At the Tokyo protest, however, hospital worker Mika Ohta vowed to vote for anti-nuclear candidates in the next election.

"There is nothing good about nuclear power. It is expensive, gets workers radiated and creates waste," she said. "I'm opposed to this government in every way."