Taliban insurgents, including at least two suicide bombers, attacked a foreign base in a city in west Afghanistan, witnesses and officials said, with several casualties feared.
The Italian-run base in Herat attacked by Taliban insurgents.
One witness reported seeing the bodies of several troops wearing foreign uniforms and saw smoke rising near an Italian-run, joint civilian and military provincial reconstruction team (PRT) base in Herat. Nato and Afghan officials were unable to confirm any casualties among Afghans or foreign troops.
A second witness told Reuters it appeared an unknown number of insurgents had entered a seven-storey building near the PRT and opened fire on the base from there.
Interior ministry spokesman Zemari Bashary said at least two suicide bombers had launched the attack outside the PRT in Herat, a normally peaceful city close to the border with Iran. He said no details about casualties were immediately available.
Taliban spokesman Qari Yousuf Ahmadi said four suicide bombers were involved, although the militant Islamists often exaggerate claims involving attacks against foreign and Afghan targets.
Italian troops form the bulk of the Nato-led International Security Assistance Force (ISAF) in the area but there was no immediate confirmation of casualties from ISAF. A spokesman for ISAF in Kabul said the force was aware of reports of the attack and was looking into them.
Television pictures from Herat showed at least two vehicles destroyed by explosions and troops scurrying for cover. Violence has spiked across Afghanistan since the Taliban announced at the beginning of May the start of a spring offensive.
Attacks have taken place in cities across Afghanistan in recent weeks. The Afghan government and security forces and foreign military targets singled out in increasingly bold assaults as militants attempt to show they retain to the capacity to launch major strikes.
US commanders had warned to expect a surge in violence as insurgents attempted to hit back after US-led ISAF troops and Afghan forces made major gains in operations in the Taliban heartland in the south over the past 12 months.
Italy has about 3,880 troops serving in Afghanistan, the majority of them in the west, making it the fifth-largest contributor to the Nato force.
Violence across Afghanistan last year reached its worst levels since the Taliban were toppled by US-backed Afghan forces in late 2001, with record civilian and military casualties.