Gen. Abul Razaq, Kandahar provincial police chief, said the attack also wounded 16 people, including three police officers and six children. The bomber detonated his explosives at a police checkpoint, he said.
Kamal Shah, a doctor at Kandahar city's Mirwais Hospital, confirmed the casualty count.
Also in the south, NATO said Tuesday that one of its service members was killed by a roadside bomb. A statement said the death occurred on Monday. It gave no further details about the soldier's nationality or where exactly the blast occurred.
A total of 544 NATO troops died in Afghanistan in 2011, the tenth year of the war. The total was considerably lower than for 2010, when more than 700 troops died.
About 840 Afghan soldiers and policemen died in 2011.