A World Health Organization consultant who was conducting a polio vaccination campaign was attacked by unknown assailants in Karachi, Pakistan, on Tuesday, the group said.

Dr. Constant Dedo, who was hired by the WHO's polio drive, was returning from a routine visit to Gadap, a town in northwestern Karachi, WHO spokeswoman Maryam Yunus said. His vehicle was intercepted by gunmen on a motorbike and shot at; the first bullets struck the tires, rendering the vehicle immobile, Yunus said.