Defence Minister Guillermo Botero said that Cadete had been bringing together dissidents to form a new group.
The government believes the ELN is holding around 10 hostages.
The watchdog body said right-wing paramilitaries were the principal culprits, blaming them for 94,754 deaths compared to 36,683 by left-wing rebels and 9,804 by government forces.
The operation in La Montañita in the southern department of Caquetá left 11 dead and two wounded.
Iván Duque won 39.7% of the votes and will face Gustavo Petro in a runoff.
Colombia's election will be held amidst a precarious security situation.
Humberto De la Calle of the Liberal Party has stated that he will do all he can to preserve the peace in Colombia if he becomes the next president.
Marlon Marín will testify to US authorities about a plot to sell 10 tonnes of cocaine to Mexico’s Sinaloa cartel.
The latest kidnappings has been claimed in a video sent by the same dissident FARC rebels who claimed responsibility for the killing of the Ecuadoran news team.
The killings are thought to be the first such abduction of journalists on Ecuadoran soil in three decades.
Ecuador's President Lenin Moreno on Thursday gave a Colombian insurgent group 12 hours to prove that two journalists and their driver, kidnapped last month on their common border, are alive or their security forces would take joint action against them.
Santrich's arrest has been swiftly denounced by the FARC, with a spokesman warning it could deal a damaging blow to the 2016 peace deal.
The suspect had been arrested on Monday in Colombia on drug trafficking charges.
Javier Ortega, Paul Rivas, and Efrain Segarra were kidnapped by FARC rebels.
Despite a peace deal with the Colombian government having been reached, the FARC dissidents did not demobilise, but joined other anti-government factions instead.
A roadside bomb has exploded as a patrol carrying out "surveillance and control" operations on the border passed by.
The election is set to be the calmest in half a century of conflict in Colombia, with the former rebel movement FARC spurning jungle warfare for politics, and the ELN observing a ceasefire.
The majority of the violence has occurred in Antioquia Department.
A number of war tribunals and truth commissions, to investigate atrocities including massacres and disappearances, are expected to begin in September.
The ELN has claimed responsibility for the attacks.