The soldiers were returning to their post after a firefight with a group of militants in Alasay district of Kapisa province late on Monday.
"Unfortunately, their vehicle hit a roadside bomb which killed six soldiers," deputy defence ministry spokesman Gen Dawlat Waziri told AFP.
"Five militants including their group leader were also killed in the firefight," he said.
No one has claimed responsibility for the attack.
Kapisa, an unstable province where French troops were stationed, lies to the northeast of Kabul close to the border with Pakistan's lawless and insurgent-infested tribal areas.
The French forces withdrew from Kapisa in 2012 and handed over security responsibility to Afghan forces.
More than 50,000 Nato combat troops still in Afghanistan are due to leave by the end of the year, and will leave the huge task of providing security to local forces.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ