Four policemen were also wounded, Ghazni police spokesman said, blaming the Taliban for the attack.
A roadside bomb tore through a passenger bus east of the Afghan capital, killing nine civilians.
The blast took place about 10:30am (05:30 GMT) on Saturday when the bus was going from Kabul to the eastern city of Ghazni, Waheedullah Jumazada, spokesman for Ghazni governor, told AFP news agency.
“Nine civilians, including three women, were killed in the explosion,” he said.
Four policemen were also wounded, Ghazni police spokesman Adam Khan Seerat said, blaming the Taliban for the attack.
There was no comment from the Taliban on the incident.
Violence on the ground has spiked in recent weeks despite the Taliban and the Afghan government holding peace talks in Qatar to end the country’s grinding war.
The top US envoy to Afghanistan, Zalmay Khalilzad, said earlier this week that fighting is threatening the peace process.
On Friday, rights group Amnesty International said at least 50 people had been killed in attacks just in the preceding week, accusing the warring sides of failing to protect civilians.
“The world must sit up and take notice. Afghan civilians are being slaughtered on a daily basis,” said the rights group’s Omar Waraich.
“The international community must make the protection of civilians a core demand for their ongoing support of the peace process.”
Afghan authorities also faced criticism this week after 11 children were killed in an air attack by the military that hit a mosque in the northeastern province of Takhar on Wednesday.
The authorities in Kabul insist that those killed were Taliban fighters operating in that area.