An Afghan soldier opened fire on American soldiers on Saturday, injuring at least seven, the US military said.
A statement by NATO-led forces said seven USA soldiers and one Afghan soldier were wounded when an Afghan army soldier opened fire at Camp Shaheen in Mazar-e Sharif.
The attacker was shot and killed and one Afghan soldier was wounded.
Al Jazeera's Rob McBride, reporting from Afghanistan's capital, Kabul, said North Atlantic Treaty Organisation soldiers were training their Afghan counterparts at the base where the attack took place.
Taliban spokesman Zabihullah Mujahid said the group took responsibility for the attack, claiming they had killed and injured tens of police officers.
American defense officials say in coming weeks they will decide whether to send between 3,000 to 5,000 more troops as requested by military commanders.
The base is the headquarters of the 209th Corps of the Afghan National Army and is located near the city of Mazar-e Sharif.
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That attack came just days after three US soldiers were killed and another wounded during a joint US-Afghan military operation in the same region.
In a separate statement, a US official said four USA military personnel were wounded. It said one Afghan soldier was killed and one wounded. One other Afghan soldier was wounded. About 5,000 non-U.S. North Atlantic Treaty Organisation forces are still in the country.
Security forces are deployed as the site of suicide attacks and an ongoing clash between Taliban insurgents and government forces in the main police station in eastern Paktia province, Afghanistan, Sunday, Jun 18, 2017. The attack Saturday at Camp Shaheen left seven American soldiers wounded, according to officials with the NATO-led mission in the country.
"A source told Al Jazeera that the attack happened at the end of a training exercise", he said.
USA troops in Afghanistan now number about 8,400, with another 5,000 from North Atlantic Treaty Organisation allies, who mainly serve in a training and advisory capacity.
If confirmed, the insider attack would be the second in a week in Afghanistan.
Defense Secretary James Mattis is set to decide in coming weeks on whether to grant the request of Army Gen. John Nicholson, the US commander in Afghanistan, to deploy betweeen 3,000 and 5,000 additional forces to the country.