"A minibus was moving on a road in Andar district when it touched off an improvised explosive device (IED). The explosion killed 18 and injured five," Deputy Provincial Governor Ali Ahmadi was quoted as saying by Xinhua.
The victims included 14 women, one child and three men.
The official said majority of the injured women were in critical condition, adding they were returning from a wedding. He blamed Taliban insurgent group for the attack.
The victims were returning from a wedding in a minibus
The Taliban has intensified attacks since they launched annual rebel offensive late April. They often attack Afghan and NATO-led forces with IEDs and roadside bombs but the lethal weapons also inflict casualties on civilians.
The UN Assistance Mission in Afghanistan recently reported that over 1,319 Afghans were killed and more than 2,500 wounded in acts of terrorism and violence in the first half of the year.