Passengers ride a packed public bus in downtown Lima, Peru, May 21, 2015. Mariana Bazo/Reuters

At least 23 people were killed and more than 30 injured in Peru when a bus in which they were traveling plunged over a ravine into a river below, authorities said on Saturday.

The passengers were traveling from the southern region of Madre de Dios towards Cusco to vote in Sunday's presidential election.

Police said the accident happened on Friday after the driver lost control as he attempted to avoid a truck swerving across the highway, bus company Civa said in a statement.

Deadly road accidents are common in Peru, where enforcement of passenger limits is minimal and many rural routes, often along high passes, are in poor condition.