Seven people, including three women and two children, were killed and eight others wounded when the car was hit while travelling in the volatile Helmand province, according to a statement by the provincial governor's office.
It said the car was one of two carrying civilians between the districts of Musa Qala and Nawzad. It hit the bomb in Musa Qala.
The statement said two other civilians were killed yesterday in a bombing in the Kajaki district, providing no other details. Insurgents also attacked a checkpoint elsewhere in the district, killing an Afghan policeman, it said.
Afghan security forces also killed 13 Taliban insurgents in Helmand's Gereshk district, according to the statement.
Elsewhere in the south, a bomb exploded near a store today, killing two civilians and wounding two others in the Spin Boldak district of Kandahar province, said Zia Durani, a spokesman for the provincial police chief.