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PLEASE NOTE: EDIT CONTAINS CONVERTED 4:3 MATERIAL The aftermath of an attack on health workers in Nigeria's Kano, where nine people were killed in two separate incidents. Gunmen on motorbikes opened fire on the workers as they administered polio vaccinations. No one has claimed responsibility - but a group of Islamist militants, who condemn Western medicine, have been blamed for recent attacks. It's the second time this year polio workers have been targeted, after a similar incident hit Pakistan in January.