A board displaying candidates of Japanese upper house election is seen outside the headquarters of Liberal Democratic Party (LDP) in Tokyo, capital of Japan, on July 10, 2016. [Photo/Xinhua]

TOKYO - Voting for the Japanese parliament's House of Councillors, or the upper house, kicked off on Sunday with the main focus on whether or not the constitution-amending forces could take an overwhelming majority in the 242-member chamber.

Half seats of the upper house are up to grab every three years. A total of 389 candidates will contest in the vote through a mix of constituencies and proportional representation.

Combined with their unchanged seats in the upper house, those parties that support Constitution amendment, including the ruling bloc that groups Prime Minister Shinzo Abe's Liberal Democratic Party (LDP) and its coalition partner of the Komeito Party, as well as two other small opposition parties, need to secure 78 positions in the contest on Sunday so as to take a two-thirds majority in the upper house.

To launch a Constitution review motion requires approval by two-thirds majority in both chambers of the Japanese bicameral parliament. The Abe-led ruling bloc already secured an overwhelming majority in the lower house.

Abe, who also serves as president of the LDP, has indicated that he plans to discuss the procedures of constitutional amendment after the election, but the revisionist stopped short of discussing the topic during the campaign to avoid losing support rate.

The ruling camp currently emphasized on promoting and pushing the prime minister's economic policy mix dubbed "Abenomics" and Abe also vowed to bring outcomes of his economic policies to benefit all people in Japan. "Abenomics" is "still halfway on the road."

Trying to stop the ruling bloc's goal, the major opposition parties enhanced their cooperation by filing joint candidates in some constituencies and called people who oppose the controversial Special Secrecy Law and unconstitutional security laws to vote against the ruling bloc.

Citing the prime minister's decision to delay the planned sales tax hike again by about 18 months, Katsuya Okada, leader of the major opposition Democratic Party, said the government economic policies are "stuck at a fork in the road" and "must be turned around."

He also criticized the newly-enacted new security laws that the constitutional pacifism is being changed by the legislation and it should not be allowed, calling for the retraction of the legislation.

The upper house election came at a time when Japan lowered the voting age from 20 to 18, that means eligible voters therefore increased by about 2.4 million.

The voting will be end at 8:00 p.m. (1100 GMT) and the results will be released possibly in the small hours on Monday. Exit polls by local media will also forecast the results after the vote.