Voters are expected to strengthen the mandate of Prime Minister Shinzo Abe in Sunday's parliamentary elections.
In what is expected to be the last national election for three years, the Japanese election will decide half of the 242 seats in the upper legislative chamber.
Although official results are not expected until Monday, an exit poll suggests that Abe has won a majority in the upper house, BBC News reported. The poll indicates that Abe's coalition will control 130 seats.
The early count showed Japan's largest opposition party, the Democratic Party, winning only 11 seats, which would mean it lost 33 of the contested seats it held before the election, the New York Times reported.
Low voter turnout may have helped Abe's well-organized party, analysts said. The government reported that voter turnout was 32.6 percent, seven percentage points lower than the last upper house election three years ago.
A win for Abe's ruling bloc — the Liberal Democratic Party and partner New Komeito — would deliver control of both chambers of parliament, according to Bloomberg.
As a result, Abe could more easily "deliver on reforms needed to cope with a rapidly graying population and bulging national debt."
Approval ratings for Abe have remained well over 60 percent since he won the premiership in a general election in December.
However, detractors call "Abenomics" a ruse, and fear that he has control over both houses of parliament he will push his conservative nationalist agenda.
At risk, they say, is Japan's constitutional commitment to pacifism, with concern in Japan and abroad of a strengthened Japanese military and more strident tone in strained relations with China and South Korea.
The Japan Daily Press reported that two major Chinese daily newspapers had criticized Abe, warning that his "dangerous politics" might disrupt the peace in the region.
Abe recently visited Ishigaki Island, near the disputed Senkaku Islands, which Tokyo and Beijing are contesting, along with other strategic areas of the South China Sea.