Five Colombian soldiers have been killed by FARC rebels, in the first major incident since peace talks between the were launched earlier this week, the army said.
The Friday night attack with explosives by rebels in the southern Putumayo region killed five soldiers and injured 10
more, said army general German Giraldo. The attack took place in a FARC stronghold near the border with Ecuador.
Rebels were armed with "unconventional explosives", the army said on its website on Sunday.
"Our hearts are with the families of the soldiers that lost their lives in this despicable attack with explosives," said
President Juan Manuel Santos.
The attack came one day after at least two suspected rebels were killed when the air force planes bombed a Revolutionary Armed Forces of Colombia (FARC) camp on the Pacific coast near the border with Panama.
"It is possible that there are more people buried [at the camp] due to the effect of the bombs," Admiral Rodolfo Amaya, the navy officer in charge of the joint military operation, told the AFP news agency on Friday.
Peace talks aimed at ending the nearly five decades of a conflict that has claimed hundreds of thousands of lives were launched formally Thursday in Oslo.
The Colombian government has refused to call a ceasefire during negotiations.
The FARC have said they are willing to discuss a ceasefire deal at any point during the peace talks.
The last attempt at talks collapsed in 2002 when authorities determined that the rebels were regrouping in a vast demilitarised zone set aside as an incentive for peace.
Founded in 1964, the FARC is Latin America's largest rebel group, with some 9,200 armed fighters. The group draws its roots from anger among landless peasants in a country with a huge divide between rich and poor.