Soldiers killed 10 National Liberation Army, or ELN, guerrillas in fighting early Sunday in Fortul, a rural area in the northeastern Colombian border province of Arauca, military spokesmen told Efe.
Two guerrillas were captured and taken to San Antonio Hospital in Tame for treatment of their wounds.
The rebels belonged to the "Comrade Castro" unit of the Domingo Lain Front, one of the ELN's most powerful units.
The front has hundreds of fighters in Arauca, the guerrilla group's main bastion, military spokesmen said.
Armed forces commander Gen. Leonardo Barrero and army commander Gen. Juan Pablo Rodriguez Barragan are en route to the area.
The government and the ELN have had contacts in recent weeks to pave the way for a peace process similar to the one that President Juan Manuel Santos's administration and the larger Revolutionary Armed Forces of Colombia, or FARC, guerrilla group have been carrying out in Havana for a year.
The ELN, which was founded in 1964 and has some 1,500 fighters, has expressed an interest for some time in holding peace talks with officials, but the government made the release of hostages being held by the rebels a condition for any talks. EFE