Pakistan polio campaign hit by fresh attacks Violence has blighted every day of the polio campaign so far: one health worker was shot dead in Karachi on Monday and four more were killed in the city with another gunned down in Peshawar on Tuesday. The bloodshed prompted the UN children's agency UNICEF and the World Health Organisation to suspend work on polio campaigns across Pakistan. UNICEF spokesman Michael Coleman told AFP the two organisations halted work in Sindh and Khyber Pakhtunkhwa provinces after Tuesday's attacks but had now extended the suspension nationwide. Rumours about polio drops being a plot to sterilise Muslims have long dogged efforts to tackle the disease in Pakistan, but suspicion of vaccination programmes intensified after the jailing of a doctor who helped the CIA find Osama bin Laden in 2011 using a hepatitis campaign. Polio cases in Pakistan fell to 28 in 2005 but have risen sharply in recent years, hitting 198 in 2011 - the highest figure for more than a decade and the most of any country in the world last year, according to the World Health Organisation. There have been 56 infections so far in 2012. There has been no claim of responsibility for this week's attacks, but in June the Taliban banned immunisations in the tribal region of Waziristan, condemning the polio campaign as a cover for espionage. In Waziristan, a hub for Islamist militants, the ban - also enforced as a protest against US drone strikes - has put the health of 240,000 children at risk, officials say. Police said Tuesday's killings in Karachi took place in suburbs dominated by Pashtuns, the dominant ethnic group in northwest Pakistan who have a sizeable migrant population in the city. Pashtuns are also disproportionately affected by polio: though the community makes up only 15 per cent of the population, it accounts for three quarters of polio cases, the WHO says.