The girl was carrying water from a river to her village home in northern Kunduz province on Wednesday when she was murdered, police spokesman Sayed Sarwar Hussaini told AFP.
“The two men attacked her and slit her throat with a knife,” he said. “They were arrested and are in police custody.”
Hussaini said one of the suspects had proposed marriage to the girl but her family had rejected the offer.
Extreme violence against women and girls remains a major problem in the conservative Muslim nation more than a decade after US-led troops brought down the notoriously brutal Taliban Islamist regime.
According to figures by British charity organisation Oxfam, 87 percent of Afghan women report having experienced physical, sexual or psychological violence or forced marriage.
Last month a 20-year-old woman was beheaded by her husband’s family in the western province of Herat after she refused to become a prostitute, police said. Four people were arrested over the brutal killing.
And in September, five people were arrested over the public flogging of a 16-year-old girl for allegedly having an affair.
The girl was whipped 100 times in front of village elders and family members in central Ghazni province. Her alleged boyfriend was fined.
Unmarried girls are often confined to the home and forbidden from maintaining any contact with men outside the immediate family.