Mayoral candidate Karina Garcia and city council candidate Yeison Obando Llanten were among six people killed in a planned attack in Colombia's southwest Cauca department, authorities have said.
The two candidates, along with three others, were traveling in an SUV when their vehicle was intercepted, shot at and subsequently set on fire.
"With sadness, we mention the candidate for the Liberal Party, it is confirmed that alias Mayinbu, who is the leader of a dissident group of the FARC ... is responsible," peace commissioner Miguel Ceballos told reporters, without elaborating on how the government had reached this conclusion.
The killing comes just days after several prominent former members of the FARC guerrilla group announced plans to take up arms once again, stepping out of the landmark 2016 peace agreement between the government and high-ranking FARC leaders.
The dissidents have accused the government of not living up to its side of the peace accord, designed to end 50 years of fighting.
Garcia was running for mayor in the October elections, hoping to represent the town of Suarez, an area that has been affected by violence rooted in drug trafficking and illegal mining.
The Cauca region where Suarez is located has been a hotbed for warring FARC and ELN dissident factions. Aside from the attack on the candidates, another six people were murdered in the area in the last 48 hours.
Garcia had published a video on August 28, disclosing ongoing threats against her. She had asked supporters and fellow candidates to not spread false statements about her candidacy that could put her life in danger.
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Her father, Orlando Garcia, blamed authorities for not taking the candidate's warnings seriously and demanded that authorities investigate the attack.
He added that his daughter, a city council member, had wanted to be mayor because she enjoyed working with her community and wanted to help.
In a statement, the Defense Ministry announced that a reward of nearly $44,000 (€40,000) would be given to anyone who had information leading to the capture of the two dissident leaders in the province.
The ministry confirmed that additional security and investigative personnel had been sent to the region.
jcg/cmk (EFE, dpa, AP, AFP)