Venezuela's former head of military intelligence, Hugo Carvajal - also known as "El Pollo", or The Chicken - has pleaded guilty to drug trafficking and narco-terrorism charges in the US.

US officials accused the 65-year-old of forming part of a drug-smuggling organisation made up of high-ranking members of the Venezuelan military.

The guilty plea is the latest twist in Carvajal's demise from feared spymaster to convict via his ignominious arrest in a hideout in Madrid, where he had been spotted despite donning a fake moustache and a wig.

Carvajal, who was a close ally of the late Venezuelan President Hugo Chávez, is thought to hold key information about Chávez's successor, Nicolás Maduro.

Carvajal was part of the Cartel de los Soles (Cartel of the Suns) - named after the suns which feature on the lapels of high-ranking officers in the Venezuelan military - according to a statement released by the US Attorney's Office for the Southern District of New York, where Carvajal was due to go on trial in the coming days.