(Bloomberg) -- Colombia’s government blamed the National Liberation Army, or ELN, for a car bomb attack on a police academy that killed 21 in the deadliest terror attack in Bogota in more than a decade.

Urban militias from the Marxist rebel group spent more than 10 months planning the attack, which also left 68 injured, and nearly 600 buildings damaged, according to authorities. A 1993 Nissan loaded with 80 kilos of pentolite explosive detonated at the General Santander academy in the south of the city on the morning of Jan. 17.

Colombia’s homicide rate rose last year, breaking a long downward trend, as illegal groups fought for control of territory and cocaine production. The nation’s biggest guerrilla group, the Revolutionary Armed Forces of Colombia, or FARC, handed in its weapons following a 2016 peace deal, but the smaller ELN and other drug-trafficking groups swiftly moved to occupy the areas it had abandoned.

Negotiations between the government and the ELN stalled after President Ivan Duque took office in August, insisting that the group stop carrying out terrorist attacks as a condition for talks. Duque believes there is now no space for dialogue with the rebels, Peace Commissioner Miguel Ceballos said, speaking alongside the Defense Minister.

Markets barely reacted to Thursday’s attack, with bonds and the peso little changed.

Thursday’s attack was the worst since 2003, when a bomb blast at an upmarket social club left more than 30 dead. Terrorism reached a peak during a bombing campaign by Pablo Escobar’s Medellin cartel in the 1980s and early 1990s. A bomb targeting a former Justice Minister killed three people near Bogota’s financial district in May 2012. An explosion at an upscale shopping mall in Bogota in 2017 also killed three.

Production of coca, the raw material for making cocaine, has more than tripled over the last five years, fueling violence across large swathes of the country.

The 2016 peace deal with the FARC ended a conflict that had lasted more than five decades. As talks between the government and ELN stalled last year, the group stepped up its operations, carrying out dozens of attacks on oil pipelines in rural areas.

The ELN has been fighting the state since the 1960s, and says it wants a Cuban-style revolution in Colombia. It has a presence on both sides of the Venezuelan border, and also operates in the Pacific region. The group currently has around 1,800 members, according to Sergio Guzman, director of Colombia Risk Analysis in Bogota.

“They’re trying to encroach on the vacuum of power that the FARC left and grow their significance through narco-trafficking, links to the Sinaloa cartel,” in Mexico, Guzman said. “In the past, they’ve targeted police and government installations. I’d expect that to continue and intensify.”

To contact the reporters on this story: Ezra Fieser in Bogota at efieser@bloomberg.net;Oscar Medina in Bogota at omedinacruz@bloomberg.net

To contact the editors responsible for this story: Matthew Bristow at mbristow5@bloomberg.net, Andrea Jaramillo

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