Nato says two of its soldiers have been killed in a bomb attack in Khost province in eastern Afghanistan.
The organisation did not immediately release the nationalities of those killed. Most of those serving in the area are American.
Nato said one soldier was also hurt when an improvised explosive device struck a convoy on a road between Khost town and the main regional US base.
There are about 70,000 foreign troops fighting the Taleban in the country.
The Taleban have been steadily increasing their attacks over the past three years.
The new US administration of Barack Obama has vowed to make Afghanistan a priority and has pledged tens of thousands more US troops.
Lt-Col Rumi Neilson-Green, a spokeswoman for the Nato-led International Security Assistance Force, said the type of explosive device used was not immediately clear. But Nato denied reports it was a suicide attack.
There have been a number of suicide attacks in the Khost area in recent months, most of them claimed by the Taleban.
The attack comes as the new joint US envoy for Pakistan and Afghanistan, Richard Holbrooke, is visiting the region.
He is expected to visit Afghanistan after Pakistan.
He has said Afghanistan will be "much tougher" than Iraq and that he had "never seen anything like the mess we have inherited".