According to ARY News, a man named Farhad in the Fazal Park area on Friday slit the throats of three sons of his brother with dagger.
The children identified as Azeem aged six, Waseem 3 years, and one-year old Shakeel.
The area police took the bodies of the slain children into custody, and investigating the incident.
The man fled from the crime after committing the killings. The police arrested him from Shahdara later with the crime weapon.
The motive of the crime could not be established.
Police said that the accused had killed his nephews in a fit of rage as he did not have his own children.