Kabul, Afghanistan (CNN) -- At least 25 Afghan civilians were killed when their bus hit a roadside bomb in southwestern Afghanistan on Wednesday, the provincial governor said.
Twenty more were wounded, said Gov. Ghulam Dastagir Azad of Nimroz province.
The blast hit a bus transporting civilians from Zarang to Kabul.
A convoy of NATO forces traveled from Zarang to Kabul on Tuesday, and the Taliban were aware of that, the governor said.
They planted more than 20 mines to detonate the convoy, he said. NATO forces discovered and defused them, he said.
The area does not have any police posts, and has been the site of attacks in the past.
In another attack in the same region, at least two civilians were killed when their car hit a roadside bomb.
Afghan and coalition forces, who were in the area, tried to provide medical help, the International Security Assistance Force said.
"These cowardly, murderous acts by the insurgents will not prevent us from securing a peaceful Afghanistan. We stand shoulder to shoulder with the people of Afghanistan in a fight against the enemies of this country," said Col. Rafael Torres, director of the ISAF Joint Command center.
President Hamid Karzai strongly condemned the explosion in Nimroz province. In a news statement, he called it "an action against Islam and a capital crime that God will never forgive. "