The bus, packed with passengers, was traveling between the district of Obe in Herat province and the provincial capital, local administration spokesman, Moheyddin Noori, told AFP.

"Fourteen people, all civilians, were killed and 11 others are injured. Women and children are among the casualties," he added.

The spokesman blamed the bombing on "the armed opposition groups" -- a reference to Taliban-led insurgents.

Improvised bombs, built with old ammunition, are the weapon of choice for the Taliban and other insurgents who have been fighting to topple the US-backed government of President Hamid Karzai for nearly 10 years.

But the poorly-made devices often kill civilians traveling on Afghan dirt roads between their villages and big cities.

Military officials say the makeshift bombs, also known as IEDs (improvised-explosive devices) are the main killer of troops in the US-led NATO force deployed in Afghanistan and local Afghan security forces.

The Herat explosion followed a suicide car bombing at a US-run base in the eastern province of Paktia, killing two Afghan guards.

Copyright AFP (Agence France-Presse), 2011