"Yesterday we captured... an American spy who was spying in Falcon state on the Amuay and Cardon refineries,” Maduro said in a televised address in capital Caracas on Friday.
The individual, Maduro said, was a member of the US Marine Corps who worked with the CIA in Iraq, and was captured with “heavy, specialized weapons and a large amount of cash” in the northwestern state.
The arrest took place after authorities had "discovered and dismantled" a "plan to cause an explosion" at El Palito refinery in Carabobo state, west of the capital.
Venezuelan authorities have stepped up security at all refineries in the Latin American country after the incidents.
Two former members of the US military were detained in Venezuela earlier this year after a group of mercenaries attempted to intrude into the northern state of La Guaira on speedboats. The Venezuelan military foiled the attack, killing eight of the armed men and arresting several others.