A suicide bomber detonated his explosives at the entrance to a US base in eastern Afghanistan on Saturday, killing three Afghan soldiers and one Afghan civilian, a US official said.
Initial reports indicated the bomber walked up to the first security gate outside Forward Operating Base Bermel in Paktika province, said Major Christine Nelson-Chung, a US spokeswoman.
She said three Afghan soldiers and one civilian were killed and that four Afghans were wounded, and that no Americans were hurt in the attack.
It was not immediately clear if the bomber had been trying to gain entry to the base, which is near the border with Pakistan.
Taliban insurgents have set off more than 100 suicide blasts this year, a record pace, and violence in 2007 has been the deadliest since the 2001 US-led invasion.
More than 5,200 people have died this year due to the insurgency, according to an Associated Press count based on figures from Afghan and Western officials.
Australia's prime minister, meanwhile, said more NATO powers must directly engage the Taliban to help ease the burden on Australia, the United States, Britain, Canada and the Netherlands, which all have troops in the dangerous southern and central parts of Afghanistan.
Germany, Italy, France and Spain have troops in the relatively safer northern sections, a fact that is causing a rift within NATO, and Australian Prime Minister John Howard said those countries need to help ease the burden on countries operating in the south.