Colombia's ELN rebel group was responsible for the car bomb attack against a police academy that killed at least 21 and injured dozens, Defence Minister Guillermo Botero says.
The government says a car driven by ELN explosives expert Jose Aldemar Rojas broke through checkpoints onto the grounds of Bogota's General Santander School on Thursday before it detonated, shattering windows of apartments nearby.
"A terrorist act by the ELN took those lives," Botero told reporters in Bogota on Friday.
The National Liberation Army (ELN), made up of some 2000 fighters and considered a terrorist organisation by the US and EU, began peace talks with the government of former President Juan Manuel Santos in February 2017.
However the talks have been put on hold by President Ivan Duque until the ELN frees all hostages and stops attacks.
Rojas, known by his war alias El Mocho or Kiko, had lost his hand in bomb-making activity and travelled frequently across the border to Venezuela, Botero said.
The attack was planned over about 10 months and Rojas was killed in the blast, he said.
Duque called the explosion a "crazy terrorist act" against unarmed cadets.
"We will not rest until we capture and bring to justice the terrorists involved," Duque said late on Thursday.
"I tell the criminals that social repudiation awaits them, the rejection of all Colombians and the international community."
Attorney General Nestoy Humberto Martinez said the vehicle, a grey Nissan Patrol four-wheel drive, was carrying 80 kilograms of the high explosive pentolite, which has been used in the past by Colombian guerrillas.
Car bombs were frequently used in Colombia during decades of civil war between the government and various leftist rebel groups, as well as in violence involving the Medellin drug cartel led by the late drug lord Pablo Escobar.
The worst of the war, which killed some 260,000 and left millions displaced, ended when the government reached a peace agreement with the Revolutionary Armed Forces of Colombia (FARC) in 2016.
The last major attack was in January 2018 when the ELN, the biggest rebel group that remains active, detonated a bomb in the northern port city of Barranquilla, killing five police officers and injuring dozens.
The ELN was founded by radical Catholic priests and has fought more than a dozen governments since it formed in 1964.
ELN rebel Ricardo Andres Carvajal Salgar has been captured, Martinez said.
Australian Associated Press