The bomber detonated his charge as the motorcade of the provincial governor, Asaddullah Khalid, drove through the streets of Kandahar city, said Dawood Ahmadi, the governor's spokesman.
Three civilians died in the blast and 12 were wounded, four critically, said Abdul Quayum, the administrator of the Kandahar hospital where rescue workers brought the civilians caught in the bombing.
Two vehicles of the U.S.-led coalition were nearby when the blast occurred, but there were no casualties among the foreign forces, said coalition spokesman Maj. Quentin Innis. One vehicle was damaged.
Another coalition spokesman, Maj. Scott Lundy, said the coalition troops were on a patrol and were not linked to the governor's convoy.
The suicide bomber's mangled body scorched in the wreckage of a black vehicle. A nearby coffee house was destroyed in the morning bombing.
A surge in fighting and attacks since mid-May, particularly in southern regions like Kandahar province where the Taliban are strongest, has killed more than 400 people, most of them militants.