Some soldiers have been arrested and others simply dismissed from the military, The Washington Post reported.
"It involves hundreds of soldiers," said Gen. Abdul Manan Farahi, intelligence chief at the Afghan Defense Ministry.
Farahi and other officials said they would not give details about the purge but they said soldiers without good documents or proof of loyalty to the government were being expelled from the military. They said any soldiers found to have plans for killing soldiers with the International Security Assistance Force, the NATO mission in Afghanistan, would be tried and punished.
Fifteen soldiers from the United States and other countries involved in the mission were killed in August -- the largest number of deaths since the first insider killings in 2007.