Abdul Ahid Wali Zada, the Afghan police spokesperson, said the bomb was planted near the Jama Masjid, the grand mosque dating back to the 12th century in Herat city on Tuesday.
No one has yet claimed responsibility for the attack, but these attacks have been mostly claimed by the ISIS terrorist group.
Images posted to social media showed plumes of black smoke rising above a mosque complex, Al Jazeera reported.
The reports came after a string of recent attacks in Afghanistan‘s capital, Kabul, and as President Ashraf Ghani hosted a summit on security.
On May 31, at least 150 people were killed when a truck loaded with explosives detonated in a fortified area of the city near several foreign embassies.