The girl, who has been named only as Sabera, was whipped 100 times in front of village elders and family members in Jaghuri district of Ghazni province on September 9 and is said to be in poor health.
“Police have arrested five people in connection with the case. We are investigating and we will soon be able to find who is the main person behind it,” interior ministry deputy spokesman Najeeb Danish said.
The flogging was reportedly ordered by a cleric. The girl’s alleged boyfriend was fined $1,600.
Afghanistan is an extremely conservative Muslim country, where unmarried girls are often confined to the home and forbidden from maintaining any contact with men outside the immediate family.
Public executions and flogging of alleged adulterers were common under the 1996-2001 Taliban regime.
Although significant progress has been made on women’s rights since a US-led invasion brought down the Taliban, many fear those gains are under threat as Nato troops leave and Kabul seeks peace with Islamist insurgents.