Maldives President Abdulla Yameen's nephew has been arrested amid renewed political unrest in the Indian Ocean nation after members of the president's family turned against him, criticising authoritarian reversals under his rule.

Faris Maumoon was arrested on Tuesday in the capital Male on charges of bribery, according to court documents.

A politician who defected to the opposition, Faris has been leading an effort to unseat Yameen's ally, speaker of parliament Abdulla Maseeh, who has been accused of ignoring allegations of corruption, mismanagement and rights abuses.

"The charges against Faris are clearly false," said Eva Abdulla, an opposition politician.

"Coming just four days before the vote to impeach the speaker, it marks the beginning of a campaign to reduce opposition votes by arresting and jailing lawmakers."

Yameen won a 2013 presidential election and has since been accused of reversing much of the country's democratic gains and corruption.

Faris is the son of Maumoon Abdul Gayoom, who was the Maldives president for 30 years.

The brothers, Gayoom and Yameen, fell apart after an acrimonious power struggle within the ruling party last year.

Gayoom called his son's arrest "a grave injustice" in a Twitter post and said: "All dictatorships are doomed to fail. That is the lesson of history."

Gayoom, who himself ruled with an iron fist, has joined forces with Mohamed Nasheed, whom he repeatedly jailed but who went on to become the country's first democratically elected president, in a campaign to undermine Yameen in the run-up to elections next year.

For his part, Nasheed, in a Twitter post, said Yameen was "highlighting his desperation by going after his own nephew".

A spokesman for Yameen declined to comment immediately.

Fears over stability

The clampdown has raised fears over stability and dented the Maldives' image as a tourist paradise.

Atul Keshap, the US ambassador to the Maldives, said Faris' arrest "impedes the normal function of parliament and democracy in Maldives". The UK and EU have expressed concern too.

Two other opposition politicians are also on trial on charges of bribery and terrorism.

A previous attempt to impeach Maseeh, the speaker, in March ended in chaos when Yameen ordered troops to eject several politicians from parliament.

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Then in April, the ruling party raised the number of signatures required for a no-confidence motion to 50 percent of the house, up from a third.

Yameen's administration has arrested most of the opponents who might challenge him in 2018. It also denies opposition allegations that it is trying to cover up corruption, including money laundering.

Nasheed, who currently lives in exile; a vice president; a defence minister; and another political party leader have been given lengthy prison sentences after trials on terrorism charges that were criticised for lack of due process.

The Maldives has other looming problems, including significant numbers of young people who have enlisted to fight for the Islamic State of the Iraq and Levant (ISIL) group, also known as ISIS.