Spiraling violence in Colombia sent its special forces into guerrilla-controlled areas near the Venezuela 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 about 20,000 others.
Colombian special forces aiming to regain control 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, leaving behind them ghost towns.
President suspends peace talks
The clashes have been between the National Liberation Army (ELN) and remnants of the Revolutionary Armed Forces of Colombia (FARC). The groups are fighting for dominance over coca plantations and drug trafficking routes.
The violence escalated after ELN rebels accused civilians of collaborating with their rivals, executing some in their homes.
President Gustavo Petro suspended peace talks with the ELN, accusing its members of war crimes.
The violence near the border prompted the government to declare a state of emergency and deploy 5,000 troops.
UN calls for peace
According to the United Nations, 30 people were 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 "calls for an immediate cessation of acts of violence against the civilian population."
ss/sms (AP, AFP)