Thirteen people, including civilians, were killed during a confrontation between Colombia's ELN rebels and dissidents from the now-demobilized FARC guerrilla group in a remote area known for drug trafficking, the country's ombudsman said on Tuesday.
The incident took place on Nov. 27 in the southwestern Narino region, a place where crime gangs and rebel groups are known to grow, process and smuggle coca, the base ingredient in cocaine.
A hard-won peace accord was agreed with the now-disbanded Revolutionary Armed Forces of Colombia (FARC) rebel group last year, ending some five decades of war.
But an array of FARC dissidents, National Liberation Army (ELN) rebels, right-wing ex-paramilitaries and crime gangs are still active in Colombia, competing for control of lucrative illegal mines and drug trafficking routes.
In Narino, fighters from the ELN attacked members of the Rural Resistance, ombudsmen Carlos Alfonso Negret said in a report. The Rural Resistance are FARC dissidents who refused to demobilize following the peace deal.
"The ombudsman's office visited the area and was able to determine that there was an exchange of fire between the group that calls itself Rural Resistance and the ELN," Negret told journalists. "There was crossfire that killed 13 people."
Neither the report nor Negret specified how many of the dead were civilians.
More than 11,000 fighters and collaborators from the FARC handed over their weapons this year as part of the peace accord.
The group has kept its initials in its reincarnation as a political party.
But Negret says some 800 former guerrillas did not demobilize, while other security sources and thinktanks put the number of dissident ex-FARC at between 700 and 1,300.
The ELN and the government began their first ever bilateral ceasefire in October, part of peace talks taking place in Ecuador. The ceasefire is set to run through Jan. 9 and may be extended.
The incident was a violation of the ceasefire, Negret said.
It is the second act of violence which has overshadowed the ceasefire, after the ELN admitted to killing an indigenous leader in restive Choco province.