Zia Durrani, the police spokesman for Kandahar province, says the attack took place when five suicide bombers stormed the border police headquarters at Spin Boldak, on the border with Pakistan today.
He says after the attackers entered the building, a firefight followed for about half an hour before the attackers detonated their explosives vests.
Spin Boldak links Kandahar to the Pakistani city of Quetta and is a major crossing between the two countries for people and goods.