At least five soldiers were killed and a dozen wounded in an apparent rebel attack in southwest Colombia, CNN affiliate Caracol reported Saturday, the first such attack since the rebels and the government began peace talks this week.
The attack occurred in the department of Putumayo, which straddles Colombia's border with Ecuador and Peru.
It involved explosives, according to Colombian President Juan Manuel Santos.
"Our hearts are with the families of the soldiers who lost their lives in the despicable attack," he wrote on Twitter.
The violence comes just days after the government and members of the Revolutionary Armed Forces of Colombia -- commonly known as the FARC -- began formal peace talks in Norway.
The talks are meant to bring an end to the longest-running insurgency in Latin America.
The Colombian government has said that it will continue its military operations against the FARC and will not consider a cease-fire until after a final agreement is reached.
The talks began in Norway and will continue in Havana, Cuba.
There have been sporadic attempts at peace since the 1980s. The last attempt fell apart in 2002. Then-President Andres Pastrana ceded an area the size of Switzerland to the guerrilla group but ended negotiations after rebels launched a series of attacks across the country in an apparent bid to strengthen their position.
The FARC continues to carry out kidnappings and attack security forces, though it has been severely weakened in recent years.