At least nine Colombian soldiers have been killed in an attack on an army base in Norte de Santander province.
The government says rebels from the National Liberation Army (ELN) launched homemade mortar shells at the base in the municipality of El Carmen.
The attack comes as the government and the ELN are engaged in peace talks as part of President Gustavo Petro’s plan to bring “total peace” to Colombia.
Mr Petro said the perpetrators were “still absolutely far from peace”.
Seven of the nine victims were serving their compulsory military service. Eight soldiers were also injured in the attack.
Peace negotiations have been under way between the two sides since November but so far no bilateral ceasefire has been agreed.
The area where the incident happened in an area known to be an ELN stronghold.
The attack, the deadliest since the peace talks resumed after a three-year hiatus, is another setback to President Petro’s aim to get all of Colombia’s illegal armed groups to down their weapons for good.
Last week, the government suspended the ceasefire it had agreed with Colombia’s main drug trafficking cartel, the Gulf Clan.
Mr Petro is the first left-wing politician to be elected president of Colombia.
His right-wing predecessor in office, Iván Duque, broke off talks with the ELN after the group exploded a car bomb at a police academy in the capital, Bogotá, in 2019. Twenty-two people died in that explosion.
Mr Petro has summoned the government delegation and guarantor countries involved in the peace negotiations for a meeting on Monday, at which they will discuss the future of the peace process.