Abdul Ahad Jailani, spokesman for the provincial police headquarters, said the deaths have swollen to 8, and two of the wounded are in critical situation.
There has been no immediate claim of responsibility. The Taliban via a statement have denied their involvement.
Bordering Iran, Herat is among the few relatively safer cities in Afghanistan.
In February this year, the United Nations Assistance Mission in Afghanistan (UNAMA) said in its annual report that the civilians again bore the brunt of violence in Afghanistan in 2016 that saw a large number of children among the 3,498 dead.
The report documented 11,418 conflict-related civilian casualties, including 3,498 people killed and 7,920 injured in 2016. Of these, 3,512 were children -- 923 dead and 2,589 injured, up by 24 percent from the previous highest-ever recorded figure.
More about: #Afghanistan #blast
