One policeman was killed and another injured by unknown gunmen while they were escorting a team of polio vaccinators in north-western Pakistan on Wednesday, police said.

The incident occurred in Par Hoti area of Mardan district, about 60 km north-east of Peshawar, capital of the Khyber-Pakhtunkhwa province.

“One policeman was killed and the other injured in the shooting,” Nawab Gul, an officer at the district police control, said. “The polio workers were unhurt in the attack.” The policemen were protecting a three-member polio eradication team going from door to door to administer vaccine to children as part of a three-day local campaign that began on Tuesday.

No one took responsibility for the attack but Taliban militants, who consider anti-polio vaccination as un-Islamic, have threatened to attack in the past.

In December, shootings in Khyber-Pakhtunkwa and the southern port city of Karachi killed nine health workers and shut down the nation-wide program for many weeks.

Later, the Government decided to delegate the program to the control of local administrations.

Pakistan, Afghanistan and Nigeria are the only nations in the world where polio remains prevalent.