The trio was reportedly seized in Carayaca, 35 miles from Caracas in the early hours of Monday, taking the number of detentions to more than 40. The official Twitter account of Venezuela’s Bolivarian national guard claimed the men were “terrorists who entered the country intending to provoke violence”.

On Sunday the army chief, Remigio Ceballos, announced the capture of another eight “enemies of the fatherland” who were pictured kneeling down before a cluster of rifle-toting troops.

Eight people were reportedly killed when a group of about 60 mercenaries, including two United States citizens, launched their botched sea raid on 2 May.

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One of the captured American attackers, Airan Berry, last week claimed, possibly under duress, that the group had been tasked with raiding Maduro’s presidential palace and seizing a local airport in order to spirit him out of the country. Many of the group are reportedly being held in El Helicoide, Venezuela’s most notorious political prison.

The failed raid has proved a propaganda boon for Maduro, who has long claimed he was the subject of an imperialist, US-sponsored assassination plot.

Maduro has spent the last 16 months fighting off a challenge from the young opposition leader Juan Guaidó, who more than 50 foreign governments recognize as Venezuela’s legitimate interim leader.

For Guaidó, who for a time last year looked poised to topple Maduro, recent events threaten to permanently derail his push for political change.

Guaidó has denied any involvement in the failed mission to capture Maduro. But two of his advisers, the Miami-based strategist Juan José Rendón and the opposition lawmaker Sergio Vergara, are alleged to have signed a $212m contract with Jordan Goudreau, the former Green Beret behind the raid.

Vergara and Rendón – who has admitted meeting Goudreau last year and paying him $50,000 in expenses – resigned from Guaidó’s team on Monday.

In his first interview since the incident, Guaidó tried to put on a brave face, insisting his campaign continued. “What happened last weekend,” Guaidó said, “was regrettable.”

But some suspect the opposition leader, from whom support has been gradually draining away, is running out of steam.

“I’m sure Maduro and his people are quite thrilled about the way this turned out. This really works for them,” said David Smilde, a Venezuela specialist at the Washington Office on Latin America.

“It just adds into this continual erosion of people’s perception of Guaidó as an effective leader, and they are thinking: ‘Well, maybe Maduro is not actually as much of a rube as we thought.’”