According to Ministry of Interior (MoI) officials, the militants were riding motorcycle when they opened fire on a check post near the police headquarter.
The officials further added that the militants have managed to flee the area following the attack.
In the meantime, a security official in Herat province said the gunmen have taken position in a residential house following the attack and clashes are still going on between the militants and Afghan forces.
Preliminary reports suggest at least two policemen have been killed and several others, including civilians have been injured.
Officials in Herat city hospital have confirmed that two dead bodies of policemen along with seven injured civilians were taken to the hospital so far.