Kabul, Afghanistan (CNN) -- At least 18 people were killed in southern Afghanistan on Friday when their bus rolled over an improvised explosive device, according to a governor's spokesman.
The vehicle was traveling from Nahr-e-Saraj district to Helmand's provincial capital of Lashkar Gah, said Dawood Ahmadi, a spokesman for the governor of the province.
Several others were wounded in the attack, he said.
Lashkar Gah, meaning "army barracks" in Farsi, was recently handed over to national security forces by departing NATO troops.
It is widely considered the most contentious area transferred to national forces.