Colombia’s death toll from a bus bombing in the southwestern department of Cauca rose to 20, authorities said, in one of the deadliest recent attacks on civilians as the country approaches high-stakes presidential elections.

The explosion occurred on April 25 along the Pan-American Highway in the municipality of Cajibío, when an explosive device struck a bus carrying passengers. Cauca Governor Octavio Guzmán said the victims included 15 women and five men, while 36 people were injured, three of them in intensive care. Five minors were among the wounded and are expected to recover.

“We are facing an escalation of terrorism that demands immediate responses. We demand decisive, sustained, and effective action from the national government in the face of the serious public order crisis we are experiencing," Guzman wrote on X.

Colombia’s Institute of Legal Medicine has deployed forensic specialists, including anthropologists and dentists, to identify victims, in a telling sign of the scale of the blast. The attack forms part of a broader surge in violence, with more than two dozen incidents recorded across the southwest in the preceding three days.

Military officials attributed the bombing to dissident factions of the former Revolutionary Armed Forces of Colombia (Farc), specifically networks linked to a commander known as Iván Mordisco, who runs a criminal organisation profiting from drug trafficking and illegal mining. Defence Minister Pedro Sánchez separately said authorities were offering a record reward of COP5bn (about $1.4mn) for information leading to the capture of a suspected organiser known as “Marlon," a rebel leader whose real name is Iván Jacob Idrobo Arredondo.

The United Nations High Commissioner for Human Rights condemned the attack and called for accountability, while regional authorities declared three days of mourning.

The latest attack adds to mounting pressure on President Gustavo Petro’s flagship “total peace” strategy, which has sought negotiated settlements with armed groups but has faced criticism over continued insecurity in peripheral regions. The resurgence of violence in Cauca — a key corridor linking coca-producing areas to Pacific export routes — underscores the enduring fragmentation of armed actors following the 2016 peace accord.

Security analysts warn that renewed attacks on civilian infrastructure risk undermining investor confidence in Colombia’s transport and logistics networks, particularly in regions critical to commodities exports. The timing is also politically sensitive, with the May 31 presidential vote approaching amid polarised debate over whether to deepen negotiations with rebel groups, as advocated by leftist candidate Ivan Cepeda, who is currently leading the polls, or adopt a more hardline military stance as suggested by the right-wing opposition.

Historically, electoral periods in Colombia have coincided with spikes in violence, as illegal groups seek to assert territorial control and influence local governance dynamics. The recent escalation suggests these dynamics remain entrenched, posing broader risks to governance, rural development and the stability of supply chains tied to the country’s extractive and agricultural sectors.