Karachi - Gunmen killed three health workers taking part in a polio vaccination drive in Karachi on Monday, police said, in the latest blow to efforts to stamp out the disease in Pakistan.
Attackers on motorbikes opened fire on polio teams in two separate incidents in the Qayyumabad neighbourhood in the east of Pakistan's biggest city.
The attacks came just days after the World Health Organisation warned that Pakistan's northwestern city of Peshawar was the world's "largest reservoir" of the polio virus.
Pakistan is one of only three countries in the world where polio remains endemic, along with Afghanistan and Nigeria. Efforts to stamp it out have been seriously hampered by deadly attacks on vaccination teams in recent years.
The vaccination campaign was suspended in parts of the city as a result of Monday's attacks, which police said also injured two people.
"The attackers wearing helmets were waiting for the teams on motorcycles", a police spokesperson told AFP.
Doctor Seemi Jamali, the head of the government Jinnah Hospital, confirmed to AFP that three bodies and two wounded people were taken to her hospital.
Immediately after the attack, the campaign was suspended in the east of the city and heavy contingents of police were deployed.
Militant groups see vaccination campaigns as a cover for espionage, and there are also long-running rumours about polio drops causing infertility.
According to the World Health Organisation, Pakistan recorded 91 cases of polio last year compared with 58 in 2012.