A police officer was killed when unidentified gunmen on Wednesday opened fire at a polio team in northwest Pakistan's Khyber Pakhtunkhwa province.
The police officer, Zafar Ali Jan, was providing security to polio workers in Buner District when the gunmen opened fire. Other members of the polio team remained unhurt as they were at some distance from the police official when the incident took place.
On April 23, another police officer on security duty for polio workers was killed in Bannu.
Chief Minister Khyber-Pakhtunkhwa Mehmood Khan took notice of the incident and summoned a report from the province's Inspector General (IG).
Pakistan is one of just three countries in the world, along with Afghanistan and Nigeria that have endemic polio.
Immunisation efforts have in the past been hampered by militants. They have previously alleged the immunisation campaigns are a cover for Western spies.
Local officials said they had recruited Muslim clerics to promote the immunisations for children after past programmes were met with resistance and even violence by extremists.