The blast, caused by a remotely controlled device attached to a bicycle, went off on Wednesday as a group of peacekeepers were shopping in the northern town of Kunduz, police chief Mutalib Beg said.
"It killed the shopkeeper and wounded 13 people, all of whom were civilians except a German soldier from ISAF," he said, referring to the Nato-led International Security Assistance Force.
An ISAF official in Kabul confirmed that the attack was aimed at its troops but said he had no more details.
During the past few months, Taliban fighters and their al-Qaida allies have targeted ISAF peacekeepers in attacks.
Most of the casualties have been Afghan civilians.
The ISAF has more than 9000 soldiers stationed in Afghanistan. Most of them are in Kabul and the relatively peaceful north and west, but there are plans for them to take over responsibility in the south to allow US forces to reduce their strength in Afghanistan.
During the past year, nearly 70 foreign troops have been killed, mostly in the south and east, making it one of the bloodiest periods since US-led forces overthrew a Taliban government for habouring al-Qaida leader Osama bin Ladin in 2001.