German special forces had been supporting an Afghan operation near the northern city of Baghlan when insurgents opened fire on the Afghan and NATO International Security Assistance Force troops, according to an army statement posted on its Internet site Sunday.
"In the subsequent battle damage assessment the Afghan and ISAF forces again came under fire. A German soldier was killed and a German soldier wounded," it said.
It said the troops called in air support but one soldier was fatally shot later when exploring the airstrike's damage.
It added that no information was available about losses among the Afghan forces but said "presumably" several insurgents had been killed.
No civilians were hurt according to the latest information, it said.
In Nuremberg, where the FDP party is holding its conference, a minute's silence was observed in the soldier's honour. Party leader Philipp Rösler said "Our thoughts are with his family, friends and comrades."