Image copyright AFP Image caption The existing Futenma airbase is located in a densely-populated urban area in Okinawa

An opponent of a US base relocation plan has won the Okinawa governor's election, local reports say, in another setback for the controversial proposal.

Takeshi Onaga comprehensively defeated incumbent Hirokazu Nakaima in Sunday's polls.

Mr Nakaima last year agreed that a plan to move Futenma air base to the north of the island could go ahead.

But there is widespread local opposition, and Mr Onaga wants the base moved off the island altogether.

"The governor's decision in December of last year to endorse (the current government relocation plan) was proven wrong when I won this election," he said.

"The people of Okinawa were clearly thinking differently and are demanding an alternative.

"I will do my best to cancel and withdraw the plan as I stand side-by-side with the people of Okinawa."

Image copyright EPA Image caption Mr Onaga (centre) and his supporters celebrated news of his projected victory

Local media said Mr Onaga defeated his rival by about 360,000 votes to 260,000.

Mr Nakaima had won the previous election on an anti-base platform, but then decided to back the move after the Japanese government promised the island a financial package.

Okinawa, which is Japan's southern-most prefecture, is home to about 26,000 US troops and several bases.

The row centres around the Futenma airbase, which sits in a heavily populated area of central Okinawa.

Residents want the base closed and the Japanese government has proposed moving it to a more remote northern part of Okinawa's main island, off Camp Schwab.

But local residents reject this and want the base moved off Okinawa altogether, arguing that the island hosts far more than its fair share of the US military presence in Japan.

Many residents associate the US bases with accidents and crime, and the 1995 gang-rape of a 12-year-old girl by US troops hardened local attitudes on the issue.

The result will be a setback for Prime Minister Shinzo Abe, who is thought to be planning a snap election and has worked for stronger military ties with the US.

The military bases on the island form a part of the longstanding US alliance with Japan.

There has been a US military presence on Okinawa since the end of World War Two, and Washington is lobbying strongly for the base move to go ahead.