Local officials in western Herat province said the explosion took place Wednesday morning on way to Herat-Islamqala.
The provincial governor Sayed Wahid Qitali meanwhile said a Humvee of security forces was struck by a roadside bomb in Lakhshak area near Herat-Islamqala highway.
He put the toll of casualties to two police officers killed and three others wounded.
There was no claim of responsibility for the attack l.
Following the Islamqala catastrophe, a government delegation was assigned and sent to probe into the incident.
Several people were arrested in relation to the fire devastation.
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