Gunmen kill a policeman guarding polio workers in northwestern Pakistan

A pair of gunmen on a motorcycle opened fire on Thursday and killed a policeman guarding a group of polio workers going door-to-door in a vaccination campaign in northwestern Pakistan, police said, the second attack on the country's anti-polio campaign in as many days.

The latest attack took place in Bannu, a district in the restive Khyber Pakhtunkhwa province, according to police officer Nasrullah Khan. The policeman who was gunned down was standing on a street corner and the attackers fled the scene, Khan said.

In a similar attack Wednesday in Bajur, also in Khyber Pakhtunkhwa province, a group of gunmen on motorcycles killed two people, a polio worker and a police escort.

No one has so far claimed responsibility for the two attacks, which have spread fears among the polio workers. Authorities on Monday launched a new, nationwide polio vaccination campaign amid stepped-up security to protect the polio workers.

On Monday, a roadside bomb exploded near a vehicle carrying officers assigned to protect polio workers in the district of South Waziristan, also in the same province, wounding six officers and three civilians. The militant Islamic State group later claimed responsibility for Monday’s attack.

Anti-polio campaigns in Pakistan are regularly marred by violence. Militants target vaccination teams and police assigned to protect them, falsely claiming that the campaigns are a Western conspiracy to sterilize children. Since January, Pakistan has reported 17 new cases of polio, jeopardizing decades of efforts to eliminate polio in the country.

The potentially fatal, paralyzing disease mostly strikes children under age 5 and typically spreads through contaminated water. Pakistan and Afghanistan are the only countries in which the spread of polio has never been stopped.