Thirteen people were also injured in Thursday's blast at a local market in the Panjwayi district, said Iyousef Stanezai, an interior ministry spokesman.
No Nato troops were hurt by the blast, a Nato spokesman said
However four Nato soldiers were killed six wounded during a rocket-propelled grenade attack on the outskirts of Kandahar on Thursday, the spokesman said.
Earlier on Thursday, a Canadian soldier from the Nato force was killed and four wounded in roadside bombings, also near Kandahar.
The attack, which took place just days after Nato took over security from US troops in the increasingly volatile south, is one of the bloodiest in Afghanistan for months.
Four Nato soldiers have been killed since the group assumed security control of southern Afghanistan on Monday.
Six other Nato soldiers have been killed in recent months as Nato stepped up its deployment ahead of the takeover.
The Taliban, intensifying operations in recent months, have vowed to topple President Hamid Karzai's US-backed government and drive out foreign forces.