Colombia's defense ministry said 10 National Liberation Army guerrillas were killed early Tuesday in what would be the rebel group's biggest battlefield loss since peace talks were suspended in January.
The defense ministry said a combined army and air force operation targeted a rebel column in the northwestern department of Antioquia that it said was responsible for attacks on the region's electric power grid.
The air force led the way with air strikes, which were followed by the deployment of army troops that fought for two hours with the surviving rebels, General Alberto Mejias, the head of the armed forces, told a news conference.
The defense ministry on Twitter congratulated the troops for a "bombing operation that succeeded in neutralizing 13 members of the ELN, 10 dead and three captured with war materiel."
The government of President Juan Manuel Santos suspended peace talks with the ELN in late January following a series of attacks on police stations that left six police dead and dozens more wounded.
Those attacks occurred after a bilateral ceasefire expired on January 9 amid a break in peace talks being held in Ecuador.
The ELN, the country's last guerrilla group, has about 1,500 fighters.
Colombia's biggest guerrilla group, the Revolutionary Armed Forces of Colombia, or FARC by its Spanish acronym, made peace with the government in 2016 and has since become a political party that is participating in upcoming legislative elections.
The ELN recently announced it would unilaterally observe a ceasefire March 9-13 in the run-up to the legislative elections.