CARACAS, Venezuela — The government of President Nicolás Maduro said it had thwarted an early morning "invasion" off its Caribbean coast on Sunday, alleging its intelligence forces had uncovered a plot, ambushed the attackers and captured or killed 10.

But later Sunday, former Venezuelan National Guard officer Javier Nieto Quintero and former U.S. Green Beret Jordan Goudreau released a video announcing the start of “Operation Gideon,” which they described as an effort to capture senior members of Maduro’s government, and calling on Venezuelan soldiers to join them.

Goudreau, a 43-year-old veteran of the wars in Iraq and Afghanistan who runs a security firm in Florida, said by telephone late Sunday that the operation involved “60 troops,” including two former U.S. Special Forces members, who had spirited into Venezuela by land and sea. Some, he said, had already engaged Maduro’s forces. None of his claims could be immediately verified.

Goudreau said the operation’s forces had been based in Colombia’s border region, in mobile camps where Venezuelan military defectors had been living. He would not confirm the location where the video released Sunday was shot. Goudreau and Nieto Quintero live in Florida.

Goudreau said he had sought U.S. government backing for the effort but was unsuccessful. He angrily claimed that he had discussed cooperation with the mainstream Venezuelan opposition but the opposition pulled out.

“Nothing I’m doing is illegal,” Goudreau said. “There are other people in the country who are ready to flip. They just need a catalyst.”

Maduro’s government officials said eight people were killed and two were captured in a predawn maritime incursion near the port city of La Guaira, about 18 miles from Caracas. Images broadcast on state television showed a cache of seized equipment including weapons and a helmet emblazoned with an American flag.

The government’s claims prompted a flurry of accusations and counteraccusations over the nature and backing of the alleged plot. The mainstream Venezuelan opposition, led by Juan Guaidó — who is recognized as the nation’s rightful leader by the United States and more than 50 other countries — denied any links to the La Guaira incursion, and questioned the veracity of the government’s account.

Three anti-Maduro figures familiar with Sunday’s incursion, including opposition lawmaker Hernán Alemán, linked it to a separate effort to oust Maduro organized by Venezuelan military defectors in Colombia that some think might have been infiltrated by government agents.

As part of that operation, Cliver Alcalá — a former Venezuelan Army general who was brought to the United States from Colombia in March to face narcotrafficking charges — allegedly sought to train more than 100 soldiers, mostly Venezuelan defectors, in three camps in Colombia for an incursion into Venezuela. The men involved in Sunday morning’s operation hailed from those camps, these people say.

Alcalá, who was charged alongside Maduro and other senior officials by U.S. authorities in March, is in U.S. custody. His lawyer declined to comment Sunday.

The operation involved at least three boats, though only one was captured. One of its commanders sent audio recordings to Venezuelan military and police WhatsApp groups, calling for troops to rebel and take to the streets.

Alemán, a Venezuelan lawmaker now living outside the country, said Sunday he had been involved in Alcalá’s operation in Colombia since last year. He said the group had to “make some adjustments” after a shipment of weapons destined for the camps was seized by Colombian authorities in March.

Alemán said the plan was for the boats to land at La Guaira, home to Venezuela’s main international airport and a half-hour from the capital.

“Our objective was clear,” Alemán said. “We were going to enter through La Guaira because it was the closest place to our targets.”

The events Sunday came days after the first anniversary of Guaido’s failed uprising in Caracas. The opposition leader attempted to rally troops to oust Maduro in April 2019, but few answered the call.

“What do you want us to do?” Alemán asked. “It may take five, even 10 failed attempts, but we will get rid of this government.”

Alemán and others briefed on the effort would not clarify the precise objective of Sunday’s incursion.

Néstor Reverol, Maduro’s interior minister, appeared on television Sunday morning to denounce what he called the “invasion by sea.”

“A group of terrorists, mercenaries, from Colombia” is how he described the participants. He said their purpose was the “assassination of leaders of the revolutionary government.”

U.S. officials expressed skepticism.

“The Maduro regime has been consistent in its use of misinformation in order to shift focus from its mismanagement of Venezuela,” the State Department said in a statement.

Venezuelan authorities said they confiscated 10 rifles, one Glock 9mm pistol and two AFAG machine guns. Images on television showed a pile of documents including ID cards, bank cards and an orthodontist’s receipt. Diosdado Cabello, president of the Maduro-controlled National Constituent Assembly, said eight people had been killed and two arrested, including, an “agent” of the U.S. Drug Enforcement Administration.

“Behind all of this is the United States, the Colombian oligarchy and narcotrafficking,” Cabello said.

The Colombian government denied that an “invasion” had originated in Colombia.

Cabello claimed that one of the people killed in the operation was Robert Colina, a military operative linked to Alcalá known as Pantera — Panther. Cabello blamed the “right wing,” but neither he nor other government officials immediately accused Guaidó or his opposition movement.

Alemán said Sunday’s operation was conducted without the knowledge of Guaidó or other senior opposition officials. He said they had been briefed last year on the broad outlines of the effort but did not endorse it.

The Colombian camps — described by several people familiar with them as rudimentary — were established after Guaido’s failed uprising last year. Senior opposition officials say they dismissed Alcalá’s effort as haphazard and unlikely to yield results, and in addition feared it had been infiltrated by Maduro’s agents.

Colombian authorities, meanwhile, did not take them seriously until the March seizure of a truckload of weapons destined for the camps. Before Alcalá was taken into Colombian custody in connection with the U.S. charges, he said in an interview with Colombian radio that the weapons were meant to be used in an operation near the border “against the Maduro dictatorship.” He has not specifically acknowledged the existence of the camps.

Guaidó did not immediately comment on Sunday’s events. Some in the mainstream opposition said Maduro’s government might have staged a fake operation for propaganda purposes.

Iván Simonovis, Guaido’s security commissioner, denied any involvement by Guaido’s “interim government.”

“If there are any bodies, I suspect they killed people elsewhere and brought the bodies to the coast,” Simonovis said. “I mean, a helmet with a U.S. flag? Come on. This is some kind of childish game.”

Faiola reported from Miami.