Kandahar provincial government spokesman Javeed Faisal said the attacker detonated his explosives at midmorning at the gates of the Spin Boldak crossing into Afghanistan, which is used by thousands of people every day.
In addition to the suicide bomber, he says the blast killed one border police officer and wounded one, and killed one civilian and wounded seven others.
Border police say the officer killed was the checkpoint commander, and they assume he was the target.