GRANADA, Colombia (Reuters) - 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.

The Andean country and the FARC signed a peace deal late last year after more than 52 years of war and recently extended the deadline for rebels to hand over weapons. The country’s conflict has killed more than 220,000 people.

Most fighters are now living in 26 special United Nations demobilization zones, but some units have refused to lay down their arms and are expected to continue their involvement in the cocaine trade, illegal mining and extortion.

Smaller rebel group the ELN has begun much-delayed peace talks with the government, but negotiations are expected to take years.

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Crime gangs like the Clan del Golfo, Los Pelusos and Los Puntilleros are trying to move into former rebels’ territories, Rodriguez said, despite 65,000 police and soldiers sent to secure the areas.

The Clan and the Puntilleros both count former right-wing paramilitaries among their leadership, while some members of the Pelusos are ex-fighters from another rebel group that demobilized in the early 1990s. The gangs have around 3,800 members, Rodriguez said.

“Stabilization is very complicated, very difficult. Colombians have to understand it will take time.” Rodriguez said. “I would say at a minimum in ten years we will be able to see how we’ve done and see more concrete results.”

FARC dissidents have been holding a U.N. official working on to substitute illegal crops hostage for nearly a month, while the Clan is accused of killing police officers in the north of the country.