Five more people were injured in Tuesday's improvised explosive device attack in the province's Obe district, Khaama Press reported.
Although there was no immediate claim of responsibility for the attack, local authorities blamed the Taliban, saying its insurgents frequently use IEDs as weapons of choice to target Afghan and NATO coalition security forces, the report said.
The BBC also quoted officials and police that the attack killed at least 17 people and that many of the victims were members of one family.
"One vehicle touched off an improvised explosive device in a village of Obe district Tuesday afternoon in Herat. The powerful explosion killed 12 women, four children and one man on the spot," the district's police chief Shir Agha told Xinhua News Agency.
Insurgency violence has escalated in Afghanistan since the Taliban began its summer offensive.
Roadside bombings and other insurgent attacks across Afghanistan last week killed at least 14 Afghan National Army soldiers.