KARACHI/PESHAWAR - Gunmen have killed six health workers of a nationwide polio vaccination drive, highlighting resistance to a campaign opposed by the Taliban.Four women were killed and two male workers injured in less than an hour in seemingly coordinated attacks in Karachi on Tuesday, the second day of the three-day campaign, raising fears for the safety of workers immunising children against the crippling disease.On Saturday, a man namely Umar Farooq working on a local government-WHO project was also shot dead in Sohrab Goth. A sixth worker, also a woman, was killed on Tuesday in Peshawar.Pakistan is one of only three countries where polio remains endemic, along with Afghanistan and Nigeria, but efforts to fight it have been opposed by the Taliban who banned immunisations in Waziristan in June, saying the campaign was a cover for espionage.The central and provincial governments as well as the WHO and UNICEF condemned the attacks. The Sindh and Balochistan government ordered a halt to the campaign, but Khyber Pakhtunkhwa government decided to go ahead with the immunisation programme.In a joint statement, WHO and UNICEF condemned expressed their commitment to supporting the efforts to rid the country of polio and other diseases but called on ‘leaders of the affected communities’ and all others to ‘do their utmost to protect health workers’.In Karachi, the killings happened in three different areas of the sprawling port city. Senior police officer Shahid Hayat blamed “militants (Taliban) who issued a fatwa against polio vaccination in the past” for the killings. He said one polio vaccination team was attacked in the eastern Karachi neighbourhood of Gulshan-e-Buner.Police said the gunmen ridding on a bike shot both Fahmida and Madiha once on head at point blank range and they died on the spot. But interestingly the police also claimed there were no eyewitnesses. The relatives of the deceased said there was no police accompanying the polio team.The second attack came in the Raja Tanvir Colony in Orangi Town area where, according to team in-charge Dr Shafiq, gunmen killed a woman worker on the spot while a male worker was seriously injured. A third polio team was attacked in Muhammad Khan Colony in Baldia Town. In this attack too, a woman worker was killed and a male worker was injured. Both these attacks were drive-by shootings and the killed women were identified as Kaneez and Naseema, and the injured men were named as Israr and Rashid.In a similar incident in Mathra suburbs of Peshawar, two attackers on a motorbike fired on two sisters working on vaccination, injuring 14-year-old Farzana who succumbed to injuries at the Lady Reading Hospital.