The mountains of Catatumbo in eastern Colombia are so dangerous that the police and army generally don’t stray far from their barracks for fear of snipers.

Colombia vowed "war" against left-wing guerrillas Monday, declaring a state of emergency and deploying thousands of soldiers to contain violence that killed at least 100 people and threatens to scupper the country's fragile peace process.

The ELN, which has an estimated 6,000 fighters, reportedly attacked civilians it accused of collaborating with a rival group, the FARC-EMC, shooting them in the streets, while in rural areas firefights broke out between members of both groups.

Colombia called on neighboring Venezuela Thursday to help tackle guerrillas blamed for a week of bloody violence that has displaced 40,000 people in the lawless border region.

Colombian President Gustavo Petro on Friday issued a decree that gives him emergency powers to respond to an outbreak of deadly violence between rival armed groups in the north-eastern Catatumbo region.

As deadly violence caused by territorial conflict forces tens of thousands to evacuate northeastern Colombia, the Colombian government reached out to Venezuela in hopes of forming an alliance to quell the violence on the Venezuelan border.