But armed militants also call on the government to resume peace talks broken off in January.
President Juan Manuel Santos has welcomed Colombia's National Liberation Army or ELN's announcement that it will stop what it calls 'offensive military operations' during next month's elections.
Legislative elections will take place on March 11 ahead of presidential voting in May.
Via its website, ELN said it would observe a four-day unilateral ceasefire and called on the Colombia government to resume peace talks.
Negotiations broke down in January when members of the ELN allegedly restarted attacks on security forces and pipelines.