PESHAWAR, Pakistan — A volunteer in a polio vaccination campaign was killed and her colleague wounded in an attack by militants near Peshawar on Tuesday, a district administration official said.

The volunteers were going door to door to give oral anti-polio drops to children in Sheik Muhammadi, on the southern fringes of Peshawar, when two gunmen opened fire on them and fled, according to the deputy city commissioner of Peshawar, Javed Marwat. A police official said that a search operation had begun but that no arrests had been made.

Mr. Marwat said the women had not asked to be accompanied by security.

“Probably, they thought it was good not to go with a police escort and become a target,” he said.