Army special forces and police launched an operation in Caqueta department, in which a longtime group leader Rodrigo Cadete, 52, was killed.

"Another nine guerrillas we killed; we have several captures and the fighting continues in the region," Defense chief Guillermo Botero said in a statement in Manizales.

Though some 7,000 members of the Revolutionary Armed Forces of Colombia (FARC) laid down their arms, about 1,700 are still in the insurgent struggle funded by drug money, military intelligence says.

With no unified command, dissidents operate in remote areas where they fight other groups to control drug trafficking and drug trafficking routes.

Colombia has experienced relative calm since the 2016 peace deal signed by then-president Juan Manuel Santos and FARC rebels.

With the landmark agreement turning the FARC into a political party, the smaller ELN is considered the last active rebel group in the country.

True to his election promises, President Ivan Duque, who took office last August, has taken a hard line against the ELN, including his demand they release all hostages as a prerequisite to kick-starting their peace process.