Two attackers were exchanging fire with Afghan troops Thursday after a suicide bombing on a logistics company working with NATO near an airport in western Afghanistan, officials said.
The attack on the private company happened on the outskirts of Herat city, a few hundred metres from the NATO-led International Security Assistance Force's headquarters in western Afghanistan, which is Italian-led.
There was no immediate information on any casualties.
ISAF troops were deployed to join the fightback after the attack, which raises questions about security in the relatively peaceful province four months after NATO troops passed control of security in Herat city to Afghan forces.
The July transfer was part of plans to wind down the 140,000-strong, mainly US foreign combat mission and leave the Afghan government in charge of security across the country by the end of 2014.
Noor Khan Nekzad, a regional police spokesman, said the gunmen were holed up in an office belonging to a firm working with foreign forces.
"There was a suicide bomb blast following which the two gunmen entered the facility," added provincial spokesman Mohayddin Noori.
A spokesman for the ISAF in western Afghanistan who declined to be quoted by name said the blast had happened outside the compound of the alliance's Regional Command West.
He added that an ISAF quick reaction force had been deployed but could not confirm comments by Noori that NATO helicopters were providing air support.
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 opened fire.
An AFP reporter at the scene said he saw a wounded Italian soldier being walked away from the area where the attack happened.
He added that Herat airport and the ISAF base were on one side of the road and the logistics company was on the other side, a few hundred metres away.
Attacks on contractors working with ISAF happen relatively frequently.
The Taliban, leaders of the decade-long insurgency in Afghanistan since the late 2001 US-led invasion ousted them from power, were not immediately reachable for comment.
Afghan interior ministry spokesman Siddiq Siddiqui confirmed there had been a "terrorist attack" in Herat but said he did not have further details.
The attack came the day after President Hamid Karzai told a regional conference in Istanbul that there was no hope for peace in Afghanistan without help from neighbours such as Pakistan, where insurgents have rear bases.