Polio vaccination workers gunned down in Pakistan Athar Hussain / Reuters Family members of Nasima Bibi, a female worker of an anti-polio drive campaign who was shot by gunmen, mourn at a hospital morgue in Karachi on Dec. 18. Rehan Khan / EPA A rescue worker ties the feet of one of the Polio vaccination workers at a mortuary. Reuters -- Gunmen shot five health workers on an anti-polio drive in a string of attacks in Pakistan on Tuesday, officials said, raising fears for the safety of workers immunizing children against the crippling disease. It was not clear who was behind the shootings but Taliban insurgents have repeatedly denounced the anti-polio campaign as a Western plot. Health officials suspended the immunization campaign in Karachi, Pakistan's biggest city of 18 million people. Rizwan Tabassum / AFP - Getty Images A Pakistani mother mourns over her daughter, who was killed while on the job as a polio vaccination worker, at a hospital morgue following an attack by gunmen in Karachi on Dec. 18. Gunmen on motorbikes shot dead five female Pakistani polio vaccination workers on Tuesday, police said, highlighting resistance to the country's immunization campaign. Four were killed in three different incidents in the sprawling port city and the fifth in the northwestern city of Peshawar, on the second day of a nationwide three-day drive against the disease, which is endemic in Pakistan. Fareed Khan / AP Pakistani rescue workers carry the dead body of a female polio worker, killed by unknown gunmen, at the morgue of local hospital in Karachi, Pakistan, on Dec. 18. Gunmen killed several people working on a government polio vaccination campaign in two different Pakistani cities on Tuesday, officials said. The attacks were likely an attempt by the Taliban to counter an initiative the militant group has long opposed. Images of daily life, political pursuits, religious rites and deadly violence.