A remote-controlled bomb in Kandahar missed a police convoy but did kill two civilians and wounded three others.
Tuesday's attack is the third major bombing in Kandahar province in the past three days.
One observer warned the blasts could be a sign that the Taliban are changing tactics in their battle against NATO forces and the central government in Kabul.
"They're certainly stepping up their attacks against even softer targets and not even worrying about collateral damage," military analyst Scott Taylor, publisher of Esprit de Corps magazine, told Canada AM on Tuesday.
Monday's blast in Spin Boldak, near the Pakistan border, targeted a Canadian military convoy.
However, at least 38 civilians died while only four Canadian soldiers received minor injuries.
On Sunday, a suicide bomber attacked a group gathered to watch dogfights on the outskirts of Kandahar. More than 100 are estimated to have died, with at least 30 police officers in that group.
Taylor said Sunday's blast was targeted against a particular faction within the police in Kandahar.
The main target is believed to have been Abdul Hakim Jan, a local militia leader.
In pre-Taliban days, Jan was known as "Commander Blue" and was considered a brute. When the Taliban rose to power in the mid-1990s, Jan fled for northern Afghanistan, Taylor said.
However, NATO saw him as an anti-Taliban ally and brought him back to the Kandahar area after the Taliban were deposed in late 2001 and gave him power and resources, he said.
"I visited him in January last year, saw his compound and realized then there was probably trouble brewing," he said, adding that in Afghanistan, "memories are long and forgiveness is short."
The Taliban claims it didn't carry out Sunday's bombing, and Taylor said it's possible the attack was more of a "personal take-out."
Kandahar is the most violent province in Afghanistan, and is the Taliban's homeland.
Canada has 2,500 troops in Kandahar province, and is actively lobbying NATO to supply it with another 1,000-soldier battle group.
The United States has said it will send about 3,200 Marines to southern Afghanistan in April for a seven-month stint. It already has 28,000 troops serving in Afghanistan.
In 2007, Afghanistan suffered its most violent year since the Taliban fell. A record 6,500 people were killed, most of them militants.
With files from The Associated Press
