- No US troops were killed, the NATO-led mission says
- The attack comes on the heels of another one targeting US troops
The wounded troops have been evacuated for treatment, the mission said in a statement. No US troops were killed.
The attack appears to have been a "green-on-blue" act by an Afghan soldier, a coalition official told CNN.
Initially, an Afghan military spokesman said four foreign soldiers were wounded when an Afghan soldier opened fire on foreign troops in Mazar-e Sharif. That spokesman did not identify the nationality of the injured soldiers.
The NATO-led mission said it has opened an investigation.
Afghanistan's Ministry of Defense also is investigating, said Abdul Qhahar Aram, head of strategic communication and public affairs for the 209 Shahin Corps.
A massive attack in April on the same Shaheen base by Taliban militants left scores of Afghan soldiers dead.
Earlier this week,
a convoy carrying US and Afghan forces
was struck by a roadside bomb and came under small arms fire. The convoy returned fire in self-defense, and there were no US casualties, NATO said in a statement.
Last Saturday, three US soldiers were killed
and another was wounded during a joint US-Afghan military operation in Afghanistan's Achin district. The Taliban claimed responsibility for that attack.