With t-shirts, balloons and white flags, the protesters walked down an avenue to concentrate on the historic Plaza de Bolívar, in downtown Bogotá, where they honored the memory of the victims with a minute of silence and white handkerchief. Similar acts were carried out in the cities of Medellín, Cali and Barranquilla.
"It is a symbol of patriotism, of civility, of union, today we are here as simple citizens rejecting terrorism, rejecting violence, showing the world that this united country is invincible," Colombian President Iván Duque said during the march.
The attack on Thursday against the General Francisco de Paula Santander Cadet School, the training center for officers of the National Police, was committed with a car loaded with 80 kilos of explosives.
In the attack, the worst of its kind in the last 15 years in Colombia, the driver of the vehicle, which belonged to the ELN, died and 20 cadets, young people between 18 and 23 years old who aspired to become officers of the National Police.
"Colombia yes, terrorism no," "No more police or military killed by terrorism," shouted the participants in the protest, many of whom approached the police to embrace them as a sign of support.
The ELN, which has some 2,000 combatants and is considered a terrorist organization by the United States and the European Union, is radical, has a diffuse chain of command and dissent among its ranks, which according to security sources and analysts makes it difficult to reach a peace agreement.
The rebel group, founded by radical Catholic priests in 1964 and inspired by the Cuban revolution, has not accepted its responsibility in the attack so far.
Although Car Bomb attacks have been frequent in Colombia in the middle of the fight against the drug cartels and the armed conflict of more than half a century that has left 2,60,000 dead, they had diminished in part by the peace agreement signed in 2016 with the demobilized guerrilla of the FARC.