Casualty rates among the International Security Assistance Force (ISAF) have fallen over the past year, though 71 members have died so far in 2013, according to the independent icasualties.Org website.
"One ISAF service member and one ISAF civilian was killed during a direct fire attack in eastern Afghanistan today," a statement from the coalition said, adding that casualty identification would be released by national authorities.
The third death was from an improvised explosive device, the coalition said, giving no further details.
In 2012, ISAF suffered 402 casualties, down from a peak of 711 in 2010.
One civilian was also killed today by an insurgent bomb planted in a motorbicycle in the province of Ghazni with 10 other people wounded, according to the province's deputy police chief.