A roadside bomb has killed two polio vaccination workers in Pakistan's northwestern tribal region, where several attacks on such workers have taken place in the past two months.
Officials said Thursday's attack happened as two men were traveling to the village of Malikhel. A roadside bomb went off and killed them both.
On Tuesday police said gunmen killed a police officer escorting a polio vaccination team in Swabi district of Khyber Pakhtunkhwa province, as the workers went door-to-door to vaccinate children against the virus. Neither of the health workers was killed in that attack.
Gunmen in December killed nine health workers carrying out such vaccinations across Pakistan.
No one has claimed responsibility for the attacks, but in the past, the Taliban has indicated violent opposition to the vaccinations and accused health workers of being spies. There also are rumors in Pakistan that the vaccinations are meant to make Muslim children sterile.
Pakistan is one of only three countries in the world where polio is endemic. The problem is worst in the tribal regions, where militants are most active.
Some information for this report was provided by AP, AFP and Reuters.