BOGOTA (Reuters) - Colombia’s ELN rebel group was responsible for the car bomb attack against a police academy that killed at least 21 and injured dozens, President Ivan Duque said on Friday, making it almost impossible peace talks with the insurgent group can soon restart.

FILE PHOTO: Police and security personnel work at the scene where a car bomb exploded, according to authorities, in Bogota, Colombia January 17, 2019. REUTERS/Luisa Gonzalez

He called on Cuba to capture 10 National Liberation Army (ELN) commanders who are currently in Havana for the stalled peace talks.

In Thursday’s attack, a car broke through checkpoints onto the grounds of the General Santander School in the capital Bogota before it detonated, shattering windows of apartments nearby. Defense Minister Guillermo Botero said on Friday the car was driven by ELN explosives expert Jose Aldemar Rojas.

“The ELN armed terrorist group is the author of this despicable attack. This was an attack prepared and organized many months in advance. For all of Colombia today it is clear that the ELN has no genuine will for peace,” Duque said in a televised national address.

At least 20 police cadets died in the blast, as did Rojas, authorities said.

The ELN, which was formed by radical Catholic priests in 1964, has not claimed responsibility or issued a public statement.

Made up of some 2,000 fighters and considered a terrorist organization by the United States and European Union, the ELN began peace talks with the government of former President Juan Manuel Santos in early 2017, but they have been put on hold by Duque until the ELN frees its 16 hostages and stops attacks.

The car bombing - the worst in Colombia in almost 16 years - has heightened fears that a new wave of attacks could be launched in the Andean nation as a reaction to the right-wing president’s stance.

Colombians plan to march in cities nationwide on Sunday in protest against the attack.

Duque, who took office in August, pledged during his election campaign to toughen offensives against the group and drug-trafficking crime gangs that kill and kidnap civilians.

On Friday he reiterated that talks cannot restart unless the insurgent group stops all attacks, and he canceled a dispensation that allowed 10 members of the ELN negotiating team to remain free in Cuba. He asked Cuba to arrest them.

“We appreciate the solidarity expressed by the government of Cuba yesterday and today we ask you to make effective the capture of the terrorists who are in your territory and deliver them to the Colombian police authorities,” Duque said.

The Cuban government did not immediately comment on his request.

In November, Colombia asked Cuba to capture ELN rebel commander Nicolas Rodriguez and provide information about the presence of other ELN commanders in Cuban territory.

It also asked Havana to act on an Interpol Red Notice on Rodriguez. The Cuban government has not responded publicly to that request.

PLANNED ATTACK

Duque called the explosion a “crazy terrorist act” against unarmed cadets. It is the worst car bomb attack since the Revolutionary Armed Forces of Colombia (FARC) detonated a vehicle in Bogota’s upmarket El Nogal social club in 2003, killing 36 and injuring more than 200.

“We will not rest until we capture and bring to justice the terrorists involved,” he said. “I tell the criminals that social repudiation awaits them, the rejection of all Colombians and the international community.”

The vehicle, a gray Nissan Patrol SUV, was carrying an estimated 80 kilograms (176 lb) of the high explosive pentolite, which has been used in the past by Colombian guerrillas, Attorney General Nestor Humberto Martinez said on Friday.

Botero said the car was registered in Rojas’ name and that he was identified by his finger prints. He said investigators believe Rojas - who formed part of Rodriguez’s security contingent years ago - did not intend to carry out a suicide attack, and that the bomb may have been activated by a cellular phone by someone else.

Rojas, known by his war alias El Mocho or Kiko, had lost a hand in bomb-making activity and traveled frequently across the border to Venezuela, Botero said.

The attack was planned over about 10 months, he said.

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 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 FARC in 2016.