Two US citizens were detained in Venezuela on Monday on suspicion of plotting to topple President Nicolas Maduro’s government, which has accused US-backed opposition leader Juan Guaido of bankrolling the scheme.

The arrests came a day after the government said it foiled an “invasion” from the sea, killing eight assailants and capturing two others.

Maduro appeared on state television to show the passports of Luke Denman, 34, and Airan Berry, 41, and told the Venezuelan military high command that the pair are members of the US security forces.

Attorney General Tarek William Saab earlier told reporters that “mercenaries” had signed a $212 million contract with Guaido using funds “stolen” from state oil company Petroleos de Venezuela SA (PDVSA).

The US – one of more than 50 countries backing Guaido as Venezuela’s acting president as he challenges Maduro for power – has slapped sanctions on PDVSA and allowed Guaido to use funds from frozen accounts belonging to the firm’s Houston-based subsidiary Citgo Petroleum Corp.

Saab said Guaido had signed a contract with former US special forces soldier Jordan Goudreau, linked in several press reports last week to an allegedly bungled attempt to topple Maduro.

The Canadian-born Goudreau, an Iraq and Afghanistan veteran, is accused of training a mercenary force to invade Venezuela that disbanded after Colombian authorities seized a weapons shipment meant for the group.

Saab also shared on social media a video of Goudreau, who now runs a private Florida-based security firm called Silvercorp USA Inc, in which the former soldier claims an operation against Maduro’s regime is ongoing.

Guaido’s press team released a statement on Monday denying the accusations and insisting it had no agreements with private security firms.

On Sunday, Venezuela claimed a group traveling on speedboats and embarking from Colombia tried to land before dawn in the northern coastal state of La Guaira but were intercepted by the military and special police units.

Diosdado Cabello, deputy leader of the ruling Socialist Party, claimed the operation was “orchestrated” by the US and its Drug Enforcement Agency (DEA), with Colombian support.

Colombia denied any involvement, while Maduro claimed on Monday that the mission aimed to assassinate him.