Two ex-combatants with Colombia's once-largest rebel group have been shot to death while participating in a campaign event for the guerrilla's new political party.

Wilman Asprilla and Ansel Montoya were killed Tuesday night in northwestern Colombia while campaigning for a congressional candidate running under the banner of the former guerrillas' party.

The United Nations mission in Colombia is condemning the deaths and urging the government to ensure the safety of all those participating in the upcoming vote.

The former Revolutionary Armed Forces of Colombia, or FARC, has transformed into a political party as part of the peace accord that ended the region's longest-running conflict.

Former rebels are guaranteed 10 seats in Colombia's congress as part of the accord but still campaigning. The FARC's leader is slated to run for president.