Guerrillas are active in the Colombian provinces of Arauca and Norte de Santander.

ECONOMIST: Venezuela

In the Catatumbo region of Colombia's Norte de Santander department, near La Pista, some 23, 000 hectares of coca plantations are under guerrilla protection.

ECONOMIST: Colombia and its neighbours

The statement came three weeks after the ELN kidnapped a group of employees of an international mining firm, also in Norte de Santander province.

BBC: Colombia ELN kidnap victims are German pensioners

Oil has become a problem for indigenous communities such as the U'Wa, who live in the eastern provinces of Arauca, Casanare, Santander, Norte de Santander and Boyaca.

BBC: Colombia's indigenous peoples face uncertain future

In the latest battle between them this month, the paramilitaries have killed 250 civilians and forced 5, 000 others to flee in Norte de Santander, a traditional guerrilla stronghold in the country's north-east.

ECONOMIST: Colombia