Colombia is offering a record 1.4 million U.S. dollars reward for information leading to the arrest of the man accused of ordering an attack that killed 21 people Saturday and wounded dozens more.

The country's defense minister, Pedro Sanchez, said Iván Jacob Idrobo Arredondo, also known as "Marlon," was behind the bombing of a motorway in the Cauca region, in the country's southwest, as well as several other nearby attacks. 

The explosion Saturday killed at least 15 women on the busy motorway, according to the governor of Cauca, Octavio Guzmán, leaving behind the twisted metal debris of multiple vehicles by a 650-foot crater in the road.

Guzmán said the bombing was the "most brutal and ruthless attack [in the region] against the civilian population in decades."

In a video on Sanchez's Facebook page, in which the defense minister looked down on the site of the attack from a helicopter, he described Marlon as "demented" and "a terrorist" who killed "humble people who were only seeking the best."

He added they would do "everything necessary" so "this doesn't happen again."

The bomb was detonated after attackers blocked traffic with a bus and another vehicle, the head of the country's armed forces, Hugo López, said in a press conference Saturday.

The country's president, Gustavo Petro, described the attackers as "terrorists" and "fascists" in a post on X, adding, "I want our very best soldiers to confront them."

Saturday's bombing was one of 26 targeting public infrastructure in the Valle del Cauca and Cauca regions in two days, according to López. It comes with armed violence a central issue in the run-up to Colombia's presidential election on May 31.

Marlon is part of an armed group led by Colombia's most wanted man, Iván Mordisco. Described by Petro as a "drug trafficker dressed as a revolutionary," Mordisco runs the Central General Staff, one of several dissident offshoots of the now-defunct Marxist-Leninist guerrilla organization the Revolutionary Armed Forces of Colombia.

A 2016 accord between the government and the Revolutionary Armed Forces of Colombia, known by its Spanish acronym FARC, saw some 7,000 rebels disarm, but Mordisco, whose real name is Néstor Gregorio Vera Fernández, was one of the 2,000 or so self-styled rebels who refused to lay down their arms.

Saturday's bombing was one of the deadliest in Colombia since the FARC killed 36 people in the bombing of a Bogotá night club in 2003.

Another of the FARC dissident groups, the National Liberation Army, killed 21 people on a police academy campus in 2019.

Last August, Mordisco's Central General Staff killed at least 18 people in a drone attack on a helicopter and a car bombing.

El Colombiano reported Tuesday that security forces believe the arrest of four of Mordisco's brothers and the death of his girlfriend in a bombardment by the Colombian air force may have been a motivation for the recent spate of bombings. Mordisco was wounded in the same strike, El Colombiano reported. 

Saturday's attack came just over a month out from national elections in Colombia, in which voters will choose between Iván Cepeda, the successor to the left-wing current president, who is currently ahead in the polling and who favors further peace negotiations with guerrilla groups, or right-wing alternatives, who take a tougher stance on the armed fighters.

Security has been a central issue of the election campaign. The conservative front-runner Miguel Uribe Turbay was shot while out campaigning in Bogotá last June, and died two months later of his wounds.

Many of the victims of Saturday's attack were reportedly from a village near the town of Cajibío, where a vigil was held Monday, with hundreds of people dressing in white as a sign of peace.

"Please, no more death, no more violence," Joao Valencia, 42, a relative of a woman killed in the attack, told Agence France Presse, as she help up her picture.

"These kinds of women should die of old age," he added, "not have their lives taken from them in such a tragic way."