Two attackers were exchanging fire with Afghan troops after a suicide bombing near Herat airport in the west of the country on Thursday, officials said.
Noor Khan Nekzad, a regional police spokesman, said the gunmen were holed up in an office belonging to a firm working with foreign forces on logistics.
“There was a suicide bomb blast following which the two gunmen entered the facility,” added provincial spokesman Mohayddin Noori.
Interior ministry spokesman Siddiq Siddiqui confirmed there had been a “terrorist attack” in Herat but said he did not have further details.
NATO troops passed control of security in Herat city to Afghan forces in July as part of plans to wind down the US-led foreign combat mission by the end of 2014 and leave the Afghan government in charge of national security.
One witness, who did not give his name, told AFP he saw several wounded people evacuated after two men with guns and rocket-propelled grenades ran into the office, and then fired at shipping containers.