FARC rebels have killed 13 soldiers in an attack on a Colombian army patrol along the northeastern border with Venezuela, the Colombian military said.
"We regret to inform you that as the result of a FARC terrorist attack, two sergeants and 11 soldiers were killed," the Colombian army leadership said in a statement on Saturday.
The incident took place in a rural area in the Arauca department town of Tame.
Although the army did not specify the circumstances of the attack, military sources quoted by the media said it was an ambush.
"In this same terrorist act, a soldier who was wounded and evacuated from the site is being treated by medical personnel," the army statement said.
The attack came on the heels of a separate assault on Wednesday claimed by the FARC's 10th Front that left 15 soldiers dead.
And in May, a FARC attack killed 11 troops.
The government and rebels have been holding peace talks in Havana since November, with the aim of ending Latin America's longest insurgency.
Former Colombian vice president Humberto de la Calle, the lead negotiator for Bogota, said the FARC would return to the talks on Monday to "continue the discussions normally".
Colombian negotiators will return to Havana as early as Sunday, he added.
The guerrillas have proposed a bilateral ceasefire during the talks, but President Juan Manuel Santos has rejected the proposal, saying it could be used to strengthen the insurgency militarily.
The FARC, or Revolutionary Armed Forces of Colombia, is a Marxist–rebel organisation, that has been fighting the Colombian army since 1964.
The FARC claims to be an armed peasant movement with an anti-imperialism agenda inspired by Bolivarianism. The group now has about 8,000 fighters, according to the defence ministry.
A government commission last month estimated that 220,000 people have lost their lives in the near 50-year-old conflict. Other estimates run as high as 600,000 dead.