Human rights in the Maldives have "been seriously eroded and are at risk of further deterioration," according to the UK-based rights group Amnesty International.

Amnesty said on Thursday that its fact-finding mission to the Indian Ocean island found political tension in the country had been exacerbated by what it called harassment, detention and imprisonment of government opponents.

"Safeguards against human rights violations are progressively eroding and the government is failing in its duty to stop this," the group said in a news briefing.

"Serious irregularities within judicial processes have resulted in rampant violations of the right to a fair trial and a severe weakening of the fundamental principle of judicial impartiality."

Urging neighbouring India to lead diplomatic engagement with authorities in Maldives, Amnesty said the five-day mission was prompted by reports of blatant breaches of the right to a fair trial for some leading opponents of the government.

Last month, the UN and Western countries expressed concern when the Maldives authorities jailed former president Mohamed Nasheed for 13 years on anti-terrorism charges, in what his party said was a politically motivated move to silence him.

"Protests by Nasheed supporters have been met with a harsh response by the authorities," Amnesty said.

"At least 140 peaceful protesters have been arrested since February, and were only released on conditions that severely limited their rights to take part in further demonstrations.

"Those detained include at least three MPs from Nasheed’s Maldivian Democratic Party (MDP), as well as other MDP politicians."

The briefing said other non-political actors, such as atheists, have been targeted.

Government officials were not readily available to respond to the accusations.

'Gang attacks'

Amnesty said its findings were based on information gathered during the research mission which began on April 17, as well as other findings in recent months.

The group held meetings with about 20 people including lawyers, journalists, human rights activists, and political activists.

Abbas Faiz, Amnesty's Maldives researcher, told Al Jazeera that gangs have continued to attack protesters with security forces doing nothing to stop them.

"The gangs appear all of a sudden and act in visible sight of the police, many are known to demonstrators who report their names to the police, but the police take no action to stop them when they attack," Faiz said.

"While we cannot for sure say if they [the gangs] are working directly with the police, we can certainly say the police does not stop them or investigate them, indicating a degree of connivance."

The Maldives adopted a new constitution in 2008, allowing political parties to function for the first time in the county’s history.

The first multi-party elections took place in 2008, which Nasheed won.

But at the parliamentary elections in 2009, parties allied to Maumoon Abdul Gayoom gained a majority, triggering a political stalemate and opposition to Nasheed, who faced calls to quit.