Preliminary military assessment has identified the left-wing ELN as responsible for the attack in a northern province.

The attack, one of the deadliest to occur in the last several months, took place on Wednesday in the rural state of Norte de Santander, near the border with Venezuela. It came more than two weeks after the government and the ELN held a second round of ceasefire negotiations in Mexico City.

“A peace process should be earnest and accountable to Colombian society,” Colombian President Gustavo Petro said on Twitter, noting that he had called a meeting with the government’s delegates and a number of countries involved in the truce efforts. The ELN has yet to comment on the attack.

Petro has promised to pursue “total peace” and turn away from the militarised approach of his predecessors. When he took office, he pushed for negotiations to end the fighting between the Colombian government and armed groups that have been active in Colombia for decades.

Wednesday’s deadly attack could set those efforts back. Petro condemned the violence, stating that those who carried it out were “far from peace”. Seven of those killed were soldiers completing compulsory service and two were officers, he added.

Eight other soldiers were injured in the attack, which included the use of improvised explosive devices and long-range weapons.

Colombia’s internal conflict stretches back nearly six decades, with government forces, right-wing paramilitaries, organised criminal groups and left-wing rebel groups clashing for control of territory. More than 450,000 people have been killed in the fighting.

In 2016, a historic peace deal brought an end to fighting between the government and the country’s largest left-wing rebel group, the Revolutionary Armed Forces of Colombia (FARC).

In its long-awaited report, released in 2022, Colombia’s Truth Commission sharply criticised the state’s militarised approach to the drug war for prolonging the conflict.

Petro, himself a former rebel, said at the time that the conclusions could not be used to create “space for vengeance”. He called for a new approach to end the violence, with an emphasis on dialogue.

However, violence and displacement has continued to plague civilians in parts of the country where armed groups and criminal organisations fight over control of lucrative resources like drug routes and illegal mining operations.

A Red Cross report released last week found that more than 180,000 civilians had been displaced in 2022, although it also concluded that violence between the state and armed groups had dropped. It welcomed efforts to negotiate truce agreements.