Santos made the announcement on Twitter, where he said “Euclides Mora” has been killed in combat in the southern Guaviare province, a stronghold of dissident FARC guerrillas.
Mora was one of five mid-level commanders who dissented from their parent organization after the FARC had closed a peace deal with the administration of President Juan Manuel Santos in November.
The FARC subsequently expelled them and has since become a political party.
A sixth mid-level commander, “Rodrigo Cadete,” escaped his guards in Guaviare earlier this month, presumably to join the dissidents.
The post-FARC guerrillas have actively opposed counter-narcotics efforts in the coca-rich area where the FARC used to exercise territorial control.
The government has vowed to use deadly force to eliminate dissident FARC groups that have primarily formed in Guaviare and the southwestern Nariño provinces.
Santos reiterated that the message to dissident groups “is clear: surrender, on the contrary jail or a tomb is awaiting you.”