An American soldier was detained after walking off his base in southern Kandahar province and shooting at Afghan civilians, causing casualties, Western officials said Sunday.
"A United States service member was detained today in connection to an incident that resulted in Afghan casualties in Kandahar province," NATO's International Security Assistance Force (ISAF) said in a statement.
A Western official told AFP: "A soldier walks off the base in the early hours Sunday morning and starts shooting. He got back to the office and was detained."
No details of the casualties were immediately available.
Kandahar governor Toryalai Wesa told AFP: "A member of the ISAF opened fire on people which may have also caused casualties. The person has been detained by ISAF and we will send a delegation to the area to investigate this."
The shooting comes after a series of incidents in which Afghan soldiers turned their guns on American troops, killing six, in the wake of the burning of Korans at a military base.
But there was no word on what might have motivated the soldier's actions.
The US has a strong presence in Kandahar, the birthplace of the hardline Islamist Taliban which is waging an insurgency against the government of President Hamid Karzai.
The US leads some 130,000 NATO troops in Afghanistan in defence of the Karzai government.