The Colombian military has killed at least 22 suspected leftist guerrillas in a battle near the Ecuadoran border, Defense Minister Rodrigo Rivera said.
"We have dealt a serious blow" to the Revolutionary Armed Forces of Colombia (FARC) guerrillas operating in the region, Rivera said on Sunday.
The minister said he has informed President Juan Manuel Santos by phone.
He gave no figures for military casualties in the fighting which erupted early Sunday in area of southern Putumayo province.
The operations against the guerrillas come as at least 40 members of the security forces have been killed since the start of September in a string of attacks and ambushes.
Rivera said the FARC is trying to weaken President Santos, a former defense minister who replaced Alvaro Uribe on August 7.
The FARC, founded in 1964, numbers about 8,000 fighters, according to official estimates.