Two former US soldiers have been sentenced to 20 years in prison in Venezuela on charges including terrorism, after a failed bid to invade the Caribbean country last May, Attorney General Tarek William Saab said.

Luke Alexander Denman, 34, and Airan Berry, 41, "admitted" to "conspiracy, association (to commit crimes), illicit trafficking of war weapons and terrorism" over the attempted invasion, allegedly aimed at toppling President Nicolas Maduro, Saab said on Twitter around midnight Friday.

They were sentenced during a court hearing, he said, and posted photographs of vehicles, weapons and identity documents.

Denman and Berry are among the 91 people, a majority of them Venezuelan nationals, whom Venezuela says it captured in thwarting the botched May 3 incursion, which saw armed men land by boat in Macuto, less than an hour from Caracas.

Maduro claimed it was a plot to assassinate him and install opposition leader Juan Guaido in his place, and Caracas has accused US President Donald Trump of being directly responsible for the raid, in which eight attackers were allegedly killed.

The Venezuelan leader has described the raid as a "remake" of the failed 1961 Bay of Pigs invasion, when Cuban exiles covertly financed and directed by the US government attempted to overthrow then Cuba leader Fidel Castro.

Denial from Trump 

Trump has long opposed Maduro, a leftist who presides over a crumbling economy and whose re-election was widely seen as marred by irregularities.

But the US has denied any involvement in the Venezuela incident.

"If I wanted to go into Venezuela I wouldn't make a secret about it," Trump said in an interview with Fox News shortly after.

Maduro has also accused Guaido -- who in January 2019 declared himself acting president in a direct challenge to Maduro's authority -- of being Trump's accomplice in planning the invasion, a charge Guaido denies.

Despite Maduro's accusations against him, Guaido has not been charged with any crimes.

The US army has confirmed that Denman and Berry are former members of the Green Berets who were deployed to Iraq.

Lawyer Alonso Medina Roa, who said he had been granted power of attorney by the Americans' relatives to represent them, said their right to a defense had been violated after he was blocked from entering the hearing on Friday. 

US Secretary of State Mike Pompeo has said the Trump administration would work to repatriate Denman and Berry. 

The US will "use every tool that we have available to try to get them back," he told reporters in May.

The others implicated in the case are Venezuelans.