ISLAMABAD, Pakistan — A pair of unidentified gunmen killed a polio vaccinator in central Pakistan on Tuesday in yet another assault on workers who are part of a government effort to curb the disease.

Pakistan is struggling to contain the spread of polio as militant violence and a chaotic political environment hobble the campaign’s progress. At least 268 new cases of polio have been reported in the country this year.

Despite the government’s repeated vows to protect health workers, the attacks continue. Taliban militants have targeted workers across the country, accusing them of being spies for Western countries.

The latest shooting took place about 9 a.m. in Faisalabad, an industrial city in Punjab Province, on the second day of a three-day national vaccination campaign.