Friday's attack caused no casualties among the forces who are fighting a resurgent Taliban along Aghanistan's frontier with Pakistan, a US military spokesman said.

"A rocket landed in the vicinity of the coalition fire base at Zormat yesterday (Friday)," Colonel Rodney Davis told reporters at the coalition's Bagram Air Base headquarters 50km (31 miles) north of Kabul.

Zormat base, some 100km (62 miles) south of Kabul, has been attacked several times since it was set up following a major  anti-Taliban operation launched in July.

Second strike

Attackers also fired at least one rocket at a base in neighbouring Khost province.

Davis did not say who was responsible for the attacks, but similar ones have been blamed on Taliban remnants, their al-Qaeda allies or supporters of the former Afghan prime minister Gulbuddin Hekmatyar, whom Washington has declared a wanted "terrorist".

Small-calibre rockets are the weapon of choice for the Taliban fighters but they are inaccurate and rarely hit their targets or cause any casualties.

Nearly two years after the fall of the Taliban, members of the group continue regular attacks on coalition and government troops and international humanitarian organisations, particularly in its former heartland in the south and southeast of Afghanistan.

The 12,500-strong US-led force is currently hunting down Taliban and al-Qaida holdouts, mainly in the southeastern provinces bordering Pakistan.