Police chief Gen. Jorge Flores said the most seriously injured were helicoptered to Lima from the scene in Huarmey some 200 miles north of the capital.
Police say a bus owned by the company Murga Serrano strayed into the oncoming lane and slammed head-on into the first of the other two buses. The truck then plowed into the wreckage.
Survivors said it took emergency crews about three hours to reach the scene, according to local media. The government sent five medical specialists to Huarmey to help the small clinic there care for the injured.