The blast occurred three days after six Canadian troops were killed in a roadside bomb explosion, also in the south.
Those deaths were the single worst combat loss for Canada in Afghanistan.
"Having security is of no use unless a massive amount of aid is invested into the community"
Justtone, Nottingham, UK
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There are some 2,500 Canadian troops in Afghanistan in the 36,000-strong Nato force.
Meanwhile, the US is pressing its allies to contribute additional forces, equipment and other resources in Afghanistan for the Nato-led spring offensive.
Robert Gates, the US defence secretary, planned to meet military leaders from Britain, Canada, Australia, the Netherlands, Denmark and Romania late on Wednesday and Thursday.
He was not expected to offer any additional US troops, however, according to a senior US defence official.
About a half-dozen defence ministers from countries working together in the volatile southern sector of Afghanistan will discuss how to "fill those last critical pieces that are needed", said the official, who spoke on condition of anonymity because the meetings had yet to take place.
Among the needed critical pieces would be aircraft and helicopters, additional trainers for the Afghanistan security forces and some increased flexibility in how some troops can be used.
Certain forces are limited in how or where they can be used, and those restrictions have been a prime complaint by the US and Nato.
The latest violence comes as Nato and Afghan troops push on with their largest-ever anti-Taliban offensive in southern Afghanistan, Operation Achilles, launched last month to flush out Taliban fighters from the northern tip of the opium-producing Helmand province.
About 5,000 Nato and Afghan troops are engaged in the offensive.
British and Canadian troops make up the bulk of the International Security Assistance Force (ISAF) in the south of the country.
Last year saw the bloodiest fighting in Afghanistan since the Taliban were ousted from power in 2001, mainly in the southern heartland of Helmand and neighbouring Kandahar province.
Britain has said it will send another 1,400 soldiers soon - making its deployment in Afghanistan greater than in Iraq. The US has also committed an extra 3,200 soldiers.