YANGON (Reuters) - A sparsely populated cluster of Indian Ocean islands has become the unlikely focus of allegations that Myanmar's government is spiking the chances of democracy icon Aung San Suu Kyi's opposition party in next month's landmark general election.

Both the ruling Union Solidarity and Development Party (USDP) and the Nobel peace laureate's National League for Democracy (NLD) have fielded candidates on the Coco Islands, an archipelago off Myanmar's west coast and the country's smallest parliamentary constituency.

But NLD parliamentary nominee Win Min has been prevented from going to the Coco Islands, where the main installation is a naval base, making it almost impossible for him to canvas for votes in the Nov 8 poll.

The allegations undermine the semi-civilian government's insistence that the election will be Myanmar's first free and fair poll for 25 years, a milestone in its transition from military dictatorship to democracy that will be closely watched by the international community.

"I believe if they let me go there, I will win," said Mr Win Min during an interview in Yangon, where he has recently been racking up a large mobile phone bill making calls to voters on the islands about 300km away.

The Coco Islands are a restricted area and transport links are sparse. A military plane flies every two weeks from Yangon, while a navy ship and a state-owned boat also make occasional trips.

Mr Win Min said he made plans three times to visit the islands since the campaign started on Sept 8, once by boat and twice by plane. His scheduled boat trip was abruptly canceled while he was waiting to board. He was told there was no space on two subsequent flights to the island.

Mr Win Min told Reuters that he had now rented a boat and was planning to set sail on his own, leaving on the 36-hour journey from Yangon on Sunday. The government has told him that he is free to go there on his own, he said.

Mr Win Min's USDP rival Thet Swe, who until August served as commander-in-chief of the navy, has been able to campaign freely on the island.

Although there are no reliable opinion polls, the USDP - which includes many members of Myanmar's former junta - is expected to be beaten in many parts of the country by the NLD.

However, the Coco Islands seat is considered to be a relatively easy win for the ruling party because of the development projects it has rolled out there and because many of the voters are military personnel or government officials.

Western diplomats say the party has used a variety of tactics to trip up NLD candidates, but most overtly in seats where it wants to ensure a victory for its prominent leaders.

Three senior USDP officials at party headquarters in the capital, Naypyitaw, declined to comment on why only their candidate was allowed access to the Coco Islands.

Mr Thet Swe could not be reached for comment.

The Election Commission says it has no say over whether the NLD candidate can visit the islands, and the decision is up to the Yangon regional government. Officials in the government of the country's main city could not be reached for comment.

"It is quite clear they don't want us campaigning there,"said Mr Win Htein, a senior NLD official, who accused authorities of "playing volleyball" with complaints filed by his party.

Mr Win Min sent campaign materials, notebooks emblazoned with leader Aung San Suu Kyi's image and NLD headbands, on a cargo ship bound for the islands last month.

Dr Hla Tun, a retired navy surgeon, and his wife have set up an NLD branch on Great Coco, the only inhabited island in the group. They have been quietly distributing the materials, but face also face challenges.

"USDP members on the island are carrying out a whisper campaign, saying that those who vote for the NLD will get in trouble," Dr Hla Tun told Reuters by phone.

The island's population is around 1,900, according to census data. Most are military families, civil servants and workers brought to the island to construct an airport. All require permission from the authorities to come and go, a regulation that Mr Win Min says he would abolish.

"They are hungry for change," he said.