Karachi: Thousands of polio workers in Pakistan Tuesday called off the polio vaccination drive after militants gunned down three health workers, including two women, who were administering the drug in Karachi.

The killing sparked anger among polio workers who are paid meagre wages. No protection is provided to them during the campaign that was launched on Monday.

“We declare that we will not carry on the polio campaign any longer,” Khairunissa, president of Sindh Polio Workers Association, said at the Jinnah Post Graduate College (JPMC).

“Let the prime minister, president, governor and the chief minister come forward themselves to carry on the campaign,” she said.

Those killed were 24-year Aneeta, a mother of three children, Fahad, 22, and Akbari.

Attackers on motorbikes opened fire on polio teams in two separate streets in the Qayyumabad neighbourhood in the city.

Police were supposed to provide security to teams but there was none when the militants attacked.

The National Immunisation Day (NID) was launched on Monday targeting 33 million children countrywide.

The attacks came just days after the World Health Organisation (WHO) warned that Pakistan’s northwestern city of Peshawar was the world’s “largest reservoir” of the polio virus.

Pakistan is one of three countries where polio remains endemic. The other countries are 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.

Militant groups see vaccination campaigns as a cover for espionage, and there are also rumours about polio drops causing infertility.

According to the WHO, Pakistan recorded 91 cases of polio last year compared with 58 in 2012.