"An explosive device detonated on a road," Governor Octavio Guzman said on X, adding that, in addition to the deaths, over 20 people were seriously injured.
Witnesses at the scene claimed the explosion was so powerful they were thrown several meters back.
Since Friday, several attacks have been reported in Colombia, which authorities blame on defectors from the disbanded FARC guerrilla group who rejected a 2016 peace agreement with the state.
Two people were injured in a bomb attack on a military base in Cali on Friday.
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