The Taliban claimed responsibility for the suicide bombing, which came only a day after the US announced it was sending more troops to Afghanistan.
Preliminary results from Afghanistan's parliamentary election indicate that warlords who built their reputations fighting the Soviets are being dumped for a younger generation.
Afghan leaders say any effort that doesn't address election fraud and corrupt officials will fail.
With President Hamid Karzai's rivals crying foul, the incumbent may win by solid margins but lose legitimacy – which could hamper counterinsurgency efforts.
But only 200 officers in the south have been trained so far in a US-led program to stem trafficking in and out of Pakistan.