The Maldives voted on Sunday in an election in which hardline President Abdulla Yameen is expected to cement his grip on power but which opposition and international groups have criticised for a lack of transparency and suppression of dissent.

The Muslim-majority Indian Ocean nation has become a theatre of rivalry between its traditional partner, India, and China, which has backed Yameen's infrastructure drive, and prompted concern in the West about Beijing's increasing influence.

Yameen's government has jailed many of his main rivals, including former president and his half brother, Maumoon Abdul Gayoom, on charges ranging from terrorism to corruption.

More than a quarter of a million people were eligible to vote in around 400 polling booths across the coral islands, best known in the West for their luxury resorts. Yameen, 59, is seeking a second five-year term.

Hundreds of people queued outside polling stations in the capital, Male, early on Sunday. On some islands, people started queuing on Saturday night.

"I am voting to revert a mistake I made in 2013. I am voting to free President Maumoon (Gayoom)," Nazima Hassan, 44, told Reuters after voting in Male.

Abdul Rasheed Husain, 46, in Male said he cast his ballot for Yameen to take the Maldives "to the next level".

Police late on Saturday raided the main opposition campaign office saying they came to "stop illegal activities", after arresting at least five opposition supporters for "influencing voters", opposition officials said.

British Ambassador James Duaris said in a twitter message said that it was "easy to understand why so many people are concerned about what might happen on Election Day".

INTERNATIONAL MONITORS STAY AWAY

Most poll monitors including those from the European Union and the United Nations declined the government's invitation to observe the election, fearing their presence might be used to endorse Yameen's re-election even after possible vote rigging.

Transparency Maldives, one of the few election monitors on the ground which had reiterated concerns about the fairness of the electoral rules, said the vote had gone smoothly.

"Observers concluded that the polling stations were set up to ensure a secret vote in the vast majority of cases (99 percent). This was less clear in about 1 percent of all cases observed. These polling stations will be closely watched."

The opposition's joint candidate, Ibrahim Mohamed Solih, known as Ibu, told supporters he was confident of victory.

"I appeal to everyone not to allow any space for unrest tomorrow," he told a rally on Saturday. "Let the voting end peacefully and let the people decide what they want. The people are hungry for a change."

Preliminary results are expected by midnight (1900 GMT).

Yameen also urged voters to head to the polls and said he was confident of the work he had done in his first term in office to put the nation on a path of development.

The country has been in political turmoil since February, when Yameen imposed a state of emergency to annul a Supreme Court ruling that quashed the convictions of nine opposition leaders, including Mohamed Nasheed, the country's first democratically elected leader and former president.

Yameen has disregarded calls from the United Nations, several Western countries and India for an amicable solution to the crisis.

Ahead of the vote, Human Rights Watch urged foreign governments to press the Maldives to uphold democratic rights.

"Should the Maldives government fail to do so, they should impose targeted sanctions, such as those proposed by the European Union, against senior ruling party officials implicated in abuses," the New York-based group said in a statement.