The Nicaraguan ambassador to the Organization of American States (OAS) on Wednesday publicly lashed out at his country's president, describing Daniel Ortega's rule as a "dictatorship."

Ortega, the 76-year-old former leftist guerrilla, won a fourth successive election last year after all his challengers were jailed, in a vote widely dismissed as a farce.

In a surprise speech to the Washington-based OAS, Arturo McFields said that "denouncing the dictatorship of my country is not easy, but continuing to remain silent and defending the indefensible is impossible.

"I have to speak, even if my future and that of my family are uncertain," he said.

"There are no independent political parties, there are no credible elections, there is no separation of powers."

Ortega's government has started the process of pulling Nicaragua out of the OAS regional body, after it rejected his reelection.

A firebrand Marxist in his youth, Ortega first governed from 1979 to 1990 when the United States backed armed opposition to his Sandinista movement, before returning to power in 2007.

He rebranded himself as a business-friendly pragmatist, but turned increasingly authoritarian, quashing presidential term limits and seizing control of all branches of the state.

Nicaraguan President Daniel Ortega (C) is sworn in as president for a fourth straight term next to his wife and vice-president Rosario Murillo (R), during the inauguration ceremony in Managua in January 2022
Nicaraguan President Daniel Ortega (C) is sworn in as president for a fourth straight term next to his wife and vice-president Rosario Murillo (R), during the inauguration ceremony in Managua in January 2022 Venezuelan Presidency via AFP / Zurimar CAMPOS

Ahead of elections last year, dozens of opposition figures -- including all seven presidential hopefuls -- were detained on accusations of undermining "national integrity."

More than 100 others have been in jail since anti-government protests in 2018 met with a crackdown that resulted in 355 deaths and more than 100,000 people fleeing into exile, according to rights groups.

"There is no freedom to publish a simple tweet, a comment on social networks," said McFields, adding many NGOs were closed or expelled.

Main opposition figure and would-be presidential challenger Cristiana Chamorro was sentenced Monday to eight years in prison after being found guilty of financial crimes.

McFields said that he had tried to get at least 20 elderly political prisoners released, but "in the government, nobody listens and nobody speaks."

"I want to tell you that people inside and outside are tired, tired of the dictatorship and its actions, and more and more people are going to say 'enough,'" he said in the video speech.

OAS Secretary General Luis Almagro applauded McFields' "courage," saying in a tweet that "this is the ethically correct position."

The United States and European Union have imposed sanctions on Ortega, his wife who serves as his vice-president, and his associates.