Voting for the House of Councilors election began early Sunday morning in Japan. It is seen as a major test for Japanese Prime Minister Naoto Kan and the ruling Democratic Party of Japan (DPJ) which is headed by him.

Some 50,000 polling stations opened at 07:00 a.m. local time. About 100 million Japanese citizens aged 20 or older are eligible to cast ballots in Sunday's election.

The upper house election is the first national poll since the Democratic Party of Japan (DPJ) rose to power last September. A total of 437 candidates are contesting for the 121 seats in this year's election. The ruling coalition has been campaigning to secure at least 56 seats to retain a majority in the upper house.

During the campaign which started in late June, the ruling and opposition parties had engaged in hot debates over issues including a possible consumption tax hike and economic growth strategies.

Analysts said the election is going to have a great impact on whether Kan can run the government smoothly. Recent media polls revealed that the DPJ might find it hard to get 50 seats, compared to the 54 seats target set by Kan and 60 seats needed for a majority.

However, the DPJ will remain in power even if it fails to retain a majority in the election, because the party is controlling the more powerful lower house, or the House of Representatives.

Kan made a final campaign tour at Kichijoji in suburb of Tokyo, capital of Japan, on Saturday. He stressed the mission of the DPJ was to rebuild the country's fiscal and social security system to regain Japan's vitality.

The DPJ was not experienced in governing but it was remarkable in many aspects, he said. He called on the voters to continue to support the DPJ so the reform plan outlined by it could be carried on.

All polling stations will close by 08:00 p.m. local time and vote counting will begin immediately after that. Full results are due out by Monday morning.

The upper house has 242 seats, of which 96 are elected by proportional representation from a national constituency and 146 are elected from Japan's 47 prefectures. Councilors' term of office is six years.

The upper house holds elections every three years for, alternately, only half of the total 242 seats, with the other half remain uncontested until the next election. The upper house is not subject to dissolution, meaning that elected officials are basically guaranteed a full term of six years.