A spokesman for NATO's International Security Assistance Force (ISAF) said the U.S. soldier "walked back to the base and turned himself into U.S. Forces this morning", adding there had been no military operations taking place in the area when the incident occurred.
Panjwayi district is about 35 km (22 miles) west of the provincial capital Kandahar city. The district is considered the spiritual home of the Taliban and has been a hive of insurgent activity in recent years.
"I saw that all 11 of my relatives were killed, including my children and grandchildren," said a weeping Haji Samad, who said he had left his home a day earlier.
BLOOD-SPATTERED WALLS
The walls of the house were blood-splattered.
"They (Americans) poured chemicals over their dead bodies and burned them," Samad told Reuters at the scene.
Neighbors said they had awoken to crackling gunfire from American soldiers, who they described as laughing and drunk.
"They were all drunk and shooting all over the place," said neighbor Agha Lala, who visited one of the homes where killings took place.
"Their (the victims') bodies were riddled with bullets."
A senior U.S. defense official said Defense Secretary Leon Panetta "was deeply saddened to hear last night of this incident and is closely monitoring reports out of Afghanistan."
Sixteen Afghan civilians killed in U.S. shooting spree | Reuters