A suicide car bomber has attacked a police station near the Afghan border with Pakistan, killing himself and a policeman, officials say.
They said that the attack - the third in as many days - happened in the Spin Boldak district of Kandahar province.
A Taleban spokesman claimed responsibility for the attack in a phone call to the Associated Press.
Spin Boldak is seen by coalition forces as a Taleban stronghold. The US is to send reinforcements to the area soon.
Correspondents say that the border crossing between Spin Boldak and the Pakistani town of Chaman is the second most important crossing on the Afghan-Pakistan border.
The driver of the car had been trying to enter a border police compound in Spin Boldak, the border police commander for south-western Afghanistan, Sayfullah Hakim, told news agency AFP.
"Police became suspicious of the vehicle and would not let it in. They took cover. The attacker detonated and wounded five border policemen," he said.
The attack - which injured at least three other people - follows a series of suicide blasts in the eastern town of Khost on Tuesday and Wednesday which killed at least 16 people.
US President Barack Obama this week replaced the general in charge of the Afghan war and appointed a new ambassador.
His administration hopes the leadership shake-up - coupled with the deployment of 21,000 additional troops - will help reverse the militants' momentum.
Violence in Afghanistan has surged to its worst level since US-backed Afghan forces overthrew the Taleban eight years ago.