In Colombia several paramilitary and guerrilla groups formed during the 1960s and afterwards. In 1983, President Fernando Belaúnde Terry of Peru described armed attacks on his nation's anti-narcotics police as "narcoterrorism", i.e., which refers to "violence waged by drug producers to extract political concessions from the government." Pablo Escobar's ruthless violence in his dealings with the Colombian and Peruvian governments has been probably two of the best known and best documented examples of narcoterrorism. Paramilitary groups associated with narcoterrorism include the Ejército de Liberación Nacional (ELN), the Fuerzas Armadas Revolucionarias de Colombia (FARC), and the Autodefensas Unidas de Colombia (AUC). While the ELN and FARC were originally left wing revolutionary groups and the AUC was originally a right-wing paramilitary, all have conducted numerous attacks on civilians and civilian infrastructure and engaged in the drug trade. The U.S. and some European governments consider them terrorist organizations.