Military intelligence officers said that Forero led a group known as Frente 28, which is one of the many dissident factions to have sprung forth from the Revolutionary Armed Forces of Colombia (Farc).
The Farc, Colombia’s largest left-wing rebel group, signed a peace deal with the government in 2016 but some of its members did not agree to the terms of the deal and refused to lay down their arms.
These dissidents groups, which are now mainly involved in cocaine trafficking and illegal mining, are among the main driving forces behind the resurgence in violence in the country.
De la Espriella said he would take a radically different approach to defeating criminal groups in the country than his predecessor in office, Gustavo Petro.
Petro, the first left-wing politician to be elected president of Colombia, advocated what he called a “total peace” strategy, which prioritised negotiation over confrontation.
His attempts to negotiate with a number of armed groups, however, failed as members of the illegal organisations repeatedly broke ceasefires and walked away from the talks.
De la Espriella’s combative approach has been met with defiance by dissident rebel groups.
On Saturday, just a day after the was sworn into office, two explosive devices went off.
In Cauca province, a car bomb exploded at a tollbooth, injuring two security guards, and in Cesar province, a police officer was killed by explosives dropped from a drone.
In a video uploaded to social media, de la Espriella praised the military for killing Forero, who was also known as “El ruso” (The Russian), and whom he described as an explosives expert.
He added that three more alleged members of the dissident group had been killed in the military operation in a rural area in Meta province.
The president also said that soldiers had killed two alleged members of another criminal group, the Gulf Clan, in a separate offensive in Antioquia province.
De la Espriella has the backing of US President Donald Trump, who endorsed his candidacy.
On Friday, the US state department said it planned to provide $1bn (£740m) in security assistance to de la Espriella’s government.
It also welcomed Colombia into the US-led group dubbed “Shield of the Americas” – an alliance of Western Hemisphere countries which have pledged to co-operate in their fight against drug trafficking gangs and transnational crime.
