"These indiscriminate killings by the Taliban are aimed at instilling fear in the people," said Sediq Sediqqi, an interior ministry spokesman.
At least three women and a three-year-old child were among those killed.
Local officials in the remote, mountainous province of Ghor said most of the passengers were from the ethnic Hazara Shi'ite minority, but that could not be independently verified.
"The insurgents stopped two vans and after checking peoples' identifications cards, they separated 14 passengers from 32 others and shot them dead," said provincial governor Sayed Anwar Rahmati.
The Taliban, an austere Sunni militant group that ruled Afghanistan from 1996 to 2001, has been fighting US-led and Afghan forces since they were removed after the Sept 11, 2001 attacks on US targets.
The Taliban, made up mainly of ethnic Pashtuns, have often targeted Shi'ites, whom they see as infidels who deserve to die.
Many of the Hazaras - believed to be descended from Mongol invaders - suffered enormously under Taliban rule and the Shi'ite minority saw many of its communities leveled.
Many were killed and buried in mass graves or thrown into wells. Tens of thousands were jailed. They still believe they are treated as second-class citizens and that President Hamid Karzai has done little to improve their lot. REUTERS