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 spokesperson.

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.