Prime Minister Shinzo Abe's Liberal Democratic Party and its junior coalition partner, Komeito, have claimed victory in an upper house election. Exit polls showed the opposition has suffered huge losses.
According to exit polls, the coalition and allied parties have won the two-thirds "super majority" needed to enable them to begin revising Japan's pacifist postwar constitution.
Abe went into the election hoping that the coalition and a loose group of hawkish conservatives from smaller parties could control a two-thirds majority in the upper house, which they already have in the lower chamber, giving him the strength to amend the constitution.
The Japanese leader called the election a referendum on his "Abenomics" policies. He claimed victory after election results showed his party and its allies gaining half the seats in parliament's upper house.
"I'm relieved that we were able to secure more than... half the seats contested," he told private broadcaster TBS television about two hours after polls closed.
Ahead of the vote, media surveys predicted that the ruling bloc would exceed Abe's target of 61 seats, while his Liberal Democratic Party (LDP) could win a majority on its own for the first time since 1989.
Abe and his party have said they plan to rewrite Article 9 of the constitution, which renounces war and forbids Japan from threatening or using force as a means of settling international disputes.
Such a move could also have far-reaching consequences for regional stability, specifically Japan's relationships with China and North Korea.
Half the seats in the 242-member upper house were contested.
Voters have expressed misgivings about Abe's platform that includes making changes to the country's constitution, which was imposed by the United States after Japan's defeat in World War II and prohibits overseas military campaigns.
Analysts said young people, who are relatively disengaged from electoral politics and social issues, didn't participate. The country also lacks wide-ranging debate on many key issues.
"Unfortunately, not many young people go to the polls," said Takao Toshikawa, founder and editor-in-chief of "Insideline," a bi-weekly publication in Tokyo.
Shinichi Nishikawa, professor of political science at Meiji University in Tokyo, said the result should not be seen as a strong mandate since voters' choices were limited.
"Considering the current negative signs for the economy, we can say many voters reluctantly voted for ruling candidates due to the weakness of the opposition," Nishikawa told AFP. "Voters passively approved Abenomics with no alternatives."
jbh,jar/sms (Reuters, dpa)