At least 20 passengers were kidnapped from buses travelling on the Zabul-Kabul highway on Saturday morning, and most are believed to be Hazara Muslims.
According to Afghan media, at least four buses were stopped while travelling from Zabul to the capital city.
Most of the abducted passengers were Hazaras, according to Afghanistan's Khaama Press.
The incident was reminiscent of the kidnapping of 30 Hazara Muslims from a bus by Isis militants in February this year.
It also comes weeks after the beheading of seven Hazara Muslims, including women and a child, allegedly by Isis.
The crime had sparked massive protests across the country, with thousands of people coming out on the streets to demand that the Afghan government end terrorism.
Hazaras belong to the minority Shiite community and are often targeted by Sunni militants.