The boy, nicknamed Gringacho, surrendered before the authorities and said he was recruited by a criminal network in the city of Trujillo, 570 km north of Lima, when he was just 12.
He told police officials that over the past three years he had killed a total of 10 people, including a young woman who was eight months pregnant.
Gringacho asked authorities to place him in a youth prison in Trujillo. Trujillo is home to Peru's most dangerous and violent criminal groups indulging in extortion and targeted killings.