The bombing occurred close a police outpost in the 14th police district of Herat City on Friday night, said the official, who did not want to be named.
He added the fatalities included seven civilians. The bomb attack, which was confirmed by Governor Waheed Qatali, left 60 individuals wounded – some critically. The injured included a number of children.
A statement from the police headquarters, meanwhile, said that the powerful explosion also damaged several houses in the area.
But Public Health Department spokesman Mohammad Rafiq Sherzai put the toll at one dead and 23 injured — including five women.
There was no immediate claim of responsibility for the bomb attack, but Interior Ministry spokesman Tariq Arian blamed the Taliban.