Clashes between the ELN and remnants of FARC, both vying for dominance over coca plantations and drug trafficking routes, have killed more than 100 people and terrorized the region.
Spiraling violence in Colombia led the government to send its special forces into guerrilla-controlled areas near the Venezuelan border even as the UN chief expressed concern on Tuesday.
A recent surge in violence resulted in the deaths of more than 100 people and displaced some 20,000 others.
Colombian special forces seeking to regain control of the disputed territory ventured into the Catatumbo region, a mountainous area in northeastern Colombia that has become the epicenter of the violence.
Residents in border regions fled to Venezuela, abandoning their towns and villages.
UN calls for peace after guerrilla attacks
According to the United Nations, 30 people have been kidnapped and almost 1,000 remain trapped in their homes.
UN Secretary-General Antonio Guterres also expressed concern about the surging violence.
The UN chief’s spokesperson, Stephane Dujarric, said in a statement that Guterres had called “for an immediate cessation of acts of violence against the civilian population.”
