Consolidating security gains from Colombia's recent peace deal with FARC guerrillas while battling remaining leftist rebels and drug trafficking gangs will take a decade, according to the head of the armed forces.

Nearly 7,000 rebels from the Marxist Revolutionary Armed Forces of Colombia (FARC) are in the midst of a demobilization process, but dissidents from the group and fighters from the National Liberation Army (ELN) remain top targets for the military, General Juan Pablo Rodriguez told Reuters.

"Once the FARC leave, other agents of violence will try to fill their space and that is the challenge that the armed forces and the national police have - to occupy those areas, to reestablish security," Rodriguez said Thursday during a visit to Meta province, which once had heavy FARC presence.

"We are intensifying territorial control operations to prevent violent actors from arriving," he added.