TOKYO -- Yoichi Masuzoe, a former health minister backed by Japan's ruling party, won Tokyo's gubernatorial election on Sunday, defeating two candidates who had promised to end nuclear power.

Masuzoe's victory was declared in exit polls on public broadcaster NHK within minutes after voting closed. Masuzoe, 65, appeared smiling before cameras, with his supporters shouting "Banzai," and promised to make Tokyo "the No. 1 city in the world."

The ballot was widely seen as a test for Japan's public opinion on atomic power in a nation shaken by the Fukushima nuclear disaster.

But the anti-nuclear camp was divided between two candidates -- former Prime Minister Morihiro Hosokawa and human-rights lawyer Kenji Utsunomiya.

Masuzoe garnered about 30 per cent of the vote, according to NHK exit polls. Hosokawa and Utsunomiya got about 20 per cent each, indicating that if the anti-nuclear vote had been united, a win by either might have been possible.

Official vote tallies were not expected until Monday.

Masuzoe was backed by Prime Minister Shinzo Abe, who wants to restart Japan's 50 nuclear reactors that were idled following the Fukushima disaster.

Hosokawa was backed by former Prime Minister Junichiro Koizumi, who pushed for zero nuclear power.

The public has been worried about safety after the multiple meltdowns at the Fukushima Dai-ichi plant. Throngs of protesters have periodically gathered outside government buildings and marched in parks, demanding an end to nuclear power.

Tetsuro Kato, professor of political science at Waseda University in Tokyo, said that the anti-nuclear vote suffered because voters could not agree on one candidate.

"This could have worked as a key vote on nuclear power, not just about city politics," he said. "But those pushing for zero nukes failed in their strategy."

Masuzoe stressed that Tokyo needs electricity.

"The Fukushima disaster has left me without words, but reducing our dependence on nuclear power needs to be done gradually," he said after his victory.

Masuzoe appealed to voters by identifying himself with Abe's relatively successful economic policies, which have set off a Japanese stock rally, and by promising a successful 2020 Tokyo Olympics in balloting that coincided with the Sochi games.

The outgoing governor, Naoki Inose, led Tokyo's Olympic bid with great fanfare, but resigned late last year over a money scandal.