A roadside bomb planted by militants struck a vehicle, killing three vaccinators in Taliban former stronghold of southern Helmand province Tuesday, spokesman for provincial government Omar Zawak said. "The vaccinators were going to a village in Sangin district at midday today to give drops of immunity from crippling polio disease to children when their car ran over a mine, as a result, all the trio were killed,"Zawak told Xinhua. He didn't blame anyone for the attack as Sangin district has been regarded as a Taliban hotbed in the province. The anti-government armed militants killed two workers of anti- polio campaign in the neighboring Uruzgan province in November last year. Two cases of polio have been reported from Afghanistan this year, and the government has been fighting to get rid of the disease.