U.S. prosecutors on Monday formally charged the former head of Venezuela's National Guard and a former anti-drug official there with colluding with cocaine traffickers.

An indictment unsealed in federal court in Brooklyn accuses Nestor Reverol and Edilberto Molina of taking bribes in exchange for helping the traffickers by tipping them off about future raids. It also alleges that from January 2008 to December 2010, they deliberately allowed cocaine shipments to leave Venezuela and returned seized drug money to them.

Reverol, 51, once ran the National Guard, which is charged with securing the country's borders, and had been a spokesman for Venezuela's anti-drug efforts. He also is the former head of Venezuela's anti-drug agency and ally of late socialist leader Hugo Chavez.

Reverol has denied the U.S. accusations, which were first reported late last year. Molina, 53, who once worked for the anti-drug agency, hasn't spoken out. Neither is in custody.

The indictment comes as the U.S has been stepping up pressure on high-ranking members of Venezuela's socialist government for their role in making the country an important transit zone for narcotics. Several Venezuelan officials, including a former defense minister and head of military intelligence, have been indicted or sanctioned.

The Venezuelan government has regularly accused the U.S. of using drug cases to destabilize President Nicolas Maduro's rule.