TOKYO — Brushing aside widespread public opposition to avoid feared electric power shortages, Prime Minister Yoshihiko Noda ordered the reactivation of two nuclear reactors at a plant in western Japan on Saturday, making it the nation’s first plant to go back online since the crisis last year in Fukushima.

The decision to restart the Ohi nuclear plant ends the temporary freeze of Japan’s nuclear power industry, when all 50 of the country’s functional reactors were idled after the triple meltdown at the Fukushima Daiichi plant. Despite the prime minister’s vows to strengthen the Ohi plant against the same sort of huge earthquake and tsunami that knocked out the Fukushima plant in March 2011, the Japanese people have remained deeply divided on the safety of nuclear power.

Even after the prime minister made a rare appeal on June 8 on national television, opinion polls showed that more Japanese opposed restarting the Ohi plant than supported it. Mr. Noda urged the nation to return to nuclear power to avoid electricity shortages that could cause blackouts and cripple industry at a time of rising competition with China and the rest of Asia. Instead, he has supported a slow phasing out of nuclear plants over several decades, as energy alternatives are found.

Saturday’s decision was seen here as a victory for the still-powerful nuclear industry and its backers in the business world, whose political support has been crucial to the otherwise unpopular Mr. Noda. It remains to be seen how the broader public will react to the restart order. Many Japanese already believe that Mr. Noda has rushed to proclaim the Ohi plant safe despite the fact that a new earthquake-resistant control center and other safety measures at the plant are years from completion.