Legal adviser Nasrullah Stanekzai said the eight were among 16 prisoners whose execution was approved by Karzai after courts rejected their appeals, the Khaama Press reported Wednesday.
Announcement of the executions drew immediate criticism from Human Rights Watch.
"The eight hangings in a single day are a terrible step backwards for Afghanistan," said the group's Asia director, Brad Adams. "President Hamid Karzai should stop future executions and commit to a formal moratorium."
Human Rights Watch said Afghanistan's renewed use of the death penalty is troubling due to the weakness of its legal system and the failure of its courts to meet international fair trial standards.
Execution of the remaining eight death row prisoners was scheduled for Wednesday, said Stanekzai.