The passengers were kidnapped in Washer district of volatile Helmand province as they were travelling on a bus and two trucks from southern Kandahar to western Herat province. Officials said yesterday that an estimated 25 people were taken.
"Twenty-one of them have been released and are now with the police," the Helmand governor's spokesman Omar Zwak said.
Afghan army corps in southern Afghanistan said they were freed in an operation yetserday evening in Marja district of Helmand.
The insurgents had earlier said they were targeting Afghan government officials aboard the vehicles.
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"We found 21 of them innocent and released them," Taliban spokesman Qari Yousuf Ahmadi told AFP, saying six others were still being held captive, a number that could not be immediately verified by officials.
Highways in Afghanistan passing through insurgency-prone areas have become exceedingly dangerous, with the Taliban and other armed groups frequently kidnapping or killing travellers.
Earlier this month, gunmen abducted 40 people in northern Kunduz province, releasing some later, but an unknown number of others remain in Taliban captivity.