A leading Nicaraguan indigenous leader has died after being detained by the ruling authoritarian regime for nearly three years.

Brooklyn Rivera, who founded the central American nation's indigenous movement Yatama, died due to "physical and neurological deterioration" linked to a Covid-19 infection, the Nicaraguan Ministry of Health stated on Sunday.

The government, headed by President Daniel Ortega, took 15 hours to confirm the death and are refusing to release the 73-year-old's body to his family, opposition media report.

The Nicaraguan government is routinely accused of political oppression, and Rivera is one of a growing number of dissidents to die in custody.

Rivera had been arbitrarily detained when he returned to his home in Nicaragua in September 2023.

He had long fought for indigenous autonomy in Nicaragua, and had opposed Ortega's Sandinista revolutionary government in the 1980s as part of an indigenous militia that fought alongside the Contras.

Rivera's detainment was only recognised by the regime more than a year after it began, following pressure from other nations.

Little was heard of his condition until Wednesday, when the government acknowledged he had been in hospital in the capital, Managua, since early March.

It said he had been suffering from a range of conditions including "cerebral edema associated with severe neurological injury", a respiratory infection and renal failure.

Nicaragua's Ministry of Health released an image of an emaciated Rivera lying in a hospital bed being ventilated via a tube through his neck.

News of his ill health sparked renewed calls for his release.

The US State Department said Rivera had been "unjustly imprisoned", and the Nicaraguan Ministry of Health's statement was "an attempt to conceal its central role in the cruel treatment and Rivera's current conditions".

"This repression, violence and lack of humanity is abominable," it added.

Meanwhile, César Marín, Amnesty International spokesperson for the region, said: "Brooklyn Rivera must be released immediately and unconditionally.

"His critical health condition while in the custody of the Nicaraguan state confirms the extreme risk to which he has been exposed."

The Nicaraguan Ministry of Health said on Sunday that Rivera had been surrounded by several members of his family when he died.

It had earlier said he could not be transferred elsewhere due to his degenerating condition.

News of Rivera's death was met by condemnation.

Bianca Jagger, a Nicaraguan human rights activist and former wife of Rolling Stones frontman Mick Jagger, told the BBC World Service's Newshour programme that she held the Ortega regime responsible for Rivera's death.

"We're talking about a dictatorial regime," she said. "There have been many other political prisoners who have died while in the custody of the regime."

The Indigenous Youth Association of Moskitia – the ancestral region Rivera hailed from – expressed its "profound indignation at the inhuman, cruel and unjust treatment he endured in his final years".

"Keeping an elderly person deprived of their liberty for years, without sufficient guarantees of due process, and in conditions that deteriorate their physical and emotional health, is a grave concern for any society that aspires to respect human rights," it said.

"His passing occurs in circumstances that should never have happened and that will continue to generate questions, pain, and legitimate demands for truth, justice and reparations."

The Argentina-based Inter-American Legal Assistance Center for Human Rights, which supports victims of repression in Nicaragua, strongly condemned Rivera's death and said those responsible "must be held criminally accountable".

Rivera served in Nicaragua's National Assembly four times, and as a minister for autonomous development in the 1990s, according to news site Confidencial.

His political party, Yatama, later aligned itself to Ortega when he returned to power in 2007. It said a month after Rivera's detention that it had been banned from running in elections.

Ortega and his wife Rosario Murillo now hold absolute power over the country. Since returning to power, their rule has been marked by authoritarian tactics, violent repression of dissent and control of the media.