ISLAMABAD, Pakistan — A health worker supervising a polio vaccination campaign was fatally shot and two others were wounded on Saturday when gunmen opened fire at a hospital in northwestern Pakistan, officials said.

No one immediately took responsibility for the killing, but the Taliban, which accuses the United States of using a drive to eradicate polio in the country as a cover for spying, has threatened the lives of health workers who immunize children.

Pakistani officials said two gunmen riding a motorbike had opened fire at a government hospital in Matni, a suburb of Peshawar, the provincial capital of the restive Khyber-Pakhtunkhwa Province. Zahid Gul, who was overseeing the vaccination campaign, was killed and another man and a woman were wounded in the attack. The gunmen fled.

Saturday’s episode was a particular setback to the former cricket star and current opposition leader Imran Khan, whose political party controls Khyber-Pakhtunkhwa.