The incident came a day after three Nato soldiers, including a Canadian, died in other attacks in Afghanistan.
Roadside bombing

The Canadian soldier was shot on Tuesday when a patrol came under attack from fighters in Kandahar's volatile Panjwayi district, the military said.
Two other International Security Assistance Force (Isaf) soldiers were  killed on Tuesday in a roadside bombing in the eastern province of Paktia.

Their nationalities were not released but most troops in the area are American.
The Taliban claimed responsibility for the bomb blast.
It was similar to a string of attacks by the group, which was removed from government in an invasion led by the United States in late 2001.
Seventy foreign soldiers have been killed in Afghanistan this year, most of them in insurgency-linked violence.
More than 70,000 international forces, the bulk of them under Nato command, are helping the government tackle the violence.