The streets were largely empty at the time of the attack, with the city still reeling from Tuesday's deadly assault and many Kandahar residents observing the fasting month of Ramadan.
Michael Griffin, an expert on Afghanistan, told Al Jazeera: "It came five or six days after the maximum alert had passed, so it was easier to go under the radar.
"In my view, it was the Taliban, but of course, the Taliban is not a unified force. There is no such thing as a unified Taliban. It seems to be a strategy of tension during a very long, drawn out election process."
A Taliban spokesman had earlier denied responsibility for Tuesday's bombing.
Wednesday's attack comes just hours after the governor of Kandahar handed responsibility for the city's security over to the army.
The police have promised to arrest the perpetrators of Tuesday's attack in the heart of the city within 72 hours.
Kandahar is the biggest city in southern Afghanistan, an area where Taliban fighters battling the Western-backed government continue to have strongholds.
The city was the powerbase of the former Taliban government, which was ousted from power in Afghanistan by US-led troops in 2001 and replaced with Karzai's Western-backed administration.
The Taliban has struck repeatedly in recent weeks in a bloody countdown to nationwide elections last week, only the second time that war-weary Afghans have voted for a president in their history.