KURRAM AGENCY - Two polio vaccination workers were killed when their motorcycle hit a roadside planted bomb in Kurram Agency on Thursday. So far, more than a dozen polio volunteers engaged in drive against polio disease have been gunned down in last two months, officials said. The two volunteers were on their way to administer polio drops to children in Malikhel area of Kurram Agency when their motorcycle hit the bomb planted at roadside. As a result of which, both the volunteers of polio drive died on the spot, officials said.In charge of the campaign in Kurram Agency Jawad Ali while talking to media persons said that two-men team were on way to Malikhel village in upper Kurram Agency when an Improvised Explosive Device planted along the roadside went off, killing them on the spot. Later, their bodies were taken to a hospital in Parachinar, where from their bodies were dispatched to their home towns.Nobody has claimed responsibility for the attack; however, militants have banned polio vaccinations in some parts of tribal belt. In December last, eight volunteers involved in a polio vaccination campaign were gunned down in Karachi, Peshawar and Charsadda districts of Khyber Pakhtunkhwa province. Besides, on Jan 1, seven staff of a charity involved in education and health projects, including polio vaccinations, were killed in Swabi.There has been no claim of responsibility for the killings. But the Taliban last year banned polio vaccinations in the tribal region of Waziristan, condemning the campaign as a cover for espionage.