Militants targeted a polio vaccination team in northwestern Pakistan on Tuesday, killing a policeman in the latest attack on workers engaged in the campaign against the crippling disease.
The unidentified gunmen opened fire on the team at Latambar area in Karak district of Khyber- Pakthunkhwa province.
The policemen were providing security cover to the vaccinators.
A policeman patrolling the area was killed in the firing.
No group has claimed responsibility for the attack.
Pakistan and neighbouring Afghanistan are the only two remaining countries in the world where polio is endemic.
Immunisation efforts in the past have been hampered by militants. They have alleged the immunisation campaigns are a cover for Western spies.
Local officials said they had recruited Muslim clerics to promote the immunisations among children after past programmes were met with resistance and even violence by extremists.
Attacks on anti-polio campaigns increased in the years following revelations that a fake hepatitis vaccination campaign was used as a ruse by the CIA in the hunt for al-Qaeda leader Osama bin Laden, who was killed by US commandos in 2011 in Pakistan.
The latest attack comes on the second day of the anti-polio drive week.
A five-day national polio immunisation drive began from Monday to vaccinate over 40 million children.