The blast occurred at early morning when a minibus set off an improvised explosive device (IED) in Khaki Safed district in northern of provincial capital Farah city, 695km west of national capital of Kabul.
The victims were passengers of the bus. Three women and a child were among the injured. Majority of the them sustained serious wounds, according to the statement.
The Taliban insurgent group has largely been using home-made IEDs to launch suicide attacks and roadside bombings against security forces but the lethal weapons also inflict casualties on civilians, Xinhua reported.
More than 2,900 civilians were killed and nearly 5,700 wounded in conflicts and Taliban-led attacks in the war-torn country last year, figures released by UN mission in the country showed.
The officials blamed the attacks of Taliban insurgents and other armed groups for most of the civilian deaths.