Colombian authorities regard the execution of four children fighters of a breakaway rebel faction as a violation of humanitarian law.

“Recruiting and killing children and adolescents from indigenous communities are not exactly gestures of goodwill to achieve peace,” Colombia’s human rights ombudsman also said on Sunday.

The statement was a reaction to the Carolina Ramirez front’s killing of the Murui natives on the border between the southern departments of Caqueta and Amazonas for defecting.

The faction broke away from the Revolutionary Armed Forces of Colombia or FARC after the 2016 peace agreement that disarmed the powerful guerrillas.

It is currently holding a bilateral truce with the government ahead of its upcoming peace talks with the government of President Gustavo Petro.

Petro slammed the multiple murders as “an atrocious crime, a blow to peace” and warned of “measures against these actions.”

Colombia has suffered more than 50 years of armed conflict between the state and various groups of left-wing guerrillas, right-wing paramilitaries and drug traffickers.

Petro, the first leftist president in Colombia’s history, has opened talks with many of the armed groups, hoping to put an end to the violence in the world’s largest cocaine producer.