"The attack took place in the city of Kandahar near the New Kabul Bank branch," Javed Faisal, spokesman for the Kandahar provincial governor, told AFP.
He said both police and civilians waiting to collect their wages were among the victims.
"Tragically, the initial death toll shows we have six dead and 20 wounded in this crowded part of the city, and most of the victims were civilians, and they came to the bank for their daily business activities," a statement from Kandahar media office said.
There was no immediate claim of responsibility for the attack. Afghan officials often blame Taliban insurgents, who are waging a nearly 12-year war against the US-backed government of President Hamid Karzai, for such attacks.
Southern Afghanistan is considered a hotbed of the Taliban insurgency, and the militants have a strong presence in Kandahar province.
Meanwhile, a roadside bomb attack hit a civilian vehicle in Sangin district of Helmand province yesterday evening, killing 12 civilians including a woman, Helmand government spokesman Omar Zwak told AFP.
