Provincial Gov. Rohul Amin said the bomber, who struck a busy market in Dilaram district of Farah province, was a woman. But the Taliban, which claimed responsibility for the blast, identified the bomber as a man named Mullah Khalid.
Five policemen, including a district police chief, and seven civilians were among those dead, Amin said. Another 27 people, including 11 police and 16 civilians were wounded, he said.
Police tried to stop the bomber seconds before he exploded, said Younus Rasoul, another provincial official.
Rasoul gave a higher death toll, saying 15 died including 12 civilians. It was not possible to reconcile the differing figures.
Afghanistan is battling a Taliban-led insurgency that is strongest in the east and south of the country.
Militants launched more than 140 suicide bombings in the country in and many of those killed in the attacks have been civilians.
At least 1,200 peoplemostly militantshave died in insurgency- related violence in 2008, according to a tally compiled by The Associated Press. The U.N. says more than 8,000 people, most of them militants, died in insurgency-related violence in 2007.