Jelani Farhad a spokesman for the provincial governor told Ariana News that the incident has taken place at Bazar area in Awba district of Herat at around 8:30 am on Saturday.
According to him, an explosive-loaded motorbike blasted off at the area.
Meanwhile, Abdul Hakim Tamana the provincial public health director said at least five kids were killed and 20 others including the district governor for Awba were injured in the incident.
He added that all the victims were transferred to the local hospitals.
No group or individual has claimed responsibility for the attack yet.