The officials further added the incident took place in Khak-e-Safid district, killing at least 3 police officers and injuring 9 others.
A local security official speaking on the condition of anonymity said Taliban militants had planted a land mine inside the field of opium in Khak-e-Safid district.
He said the blast took place while Afghan police officers were busy with destroying the opium fields, killing two Afghan police along with an Afghan national army officer.
Farah is among the volatile region in western Afghanistan where Taliban militants and other insurgent groups are openly operating.
In the meantime the security official in Farah province said at least 3 militants were killed and 5 others were injured following a separate gun battle in this province.
Taliban militants group yet to comment regarding the incident.