Armed men have killed three more people working on a polio vaccination campaign in Pakistan, officials said, as the nationwide drive against the crippling disease suffered a third day of bloodshed.
A female health worker and her driver were shot dead in Charsadda, near Peshawar, the main town of northwest Pakistan, police official Wajid Khan told AFP news agency on Wednesday. A second police officer confirmed the incident.
Another worker shot and critically wounded in an earlier attack on the outskirts of Peshawar also died, doctor Ahmad Saqlain of the city's Lady Reading Hospital said.
On Monday and Tuesday, six female health workers were killed in attacks in the southern port city of Karachi and Peshawar. The youngest was 17-years-old.
Pakistan, one of only three countries in the world where polio remains endemic, launched a UN-backed three-day nationwide vaccination campaign on Monday.
Al Jazeera's Imtiaz Tyab, reporting from Islamabad, said the UN has ordered all staff in Pakistan involved in the polio eradication campaign to suspend work and come off the streets.
"More than 200.000 people are said to be involved in this most recent three-day programme, which is part of efforts to immunise more than 30 million children across Pakistan."
There has been no claim of responsibility for the polio worker attacks, which authorities say were co-ordinated and occurred at the same time in different parts of the country.
Senior police officer Shahid Hayat blamed "militants who issued a fatwa against polio vaccination in the past" for the killings.
In June, the Taliban banned immunisations in the tribal region of Waziristan, condemning the polio campaign as a cover for espionage.
After Tuesday's attacks, the government of Sindh province, of which Karachi is capital, halted the immunisation drive, and an official said the Khyber Pakhtunkhwa government would have no choice but to follow suit.
"We are holding an emergency meeting with our donors and we have no option but to postpone the vaccination campaign for the time being. We will formally announce it after the meeting," Janbaz Afridi, doctor in charge of the immunisation campaign in Khyber Pakhtunkhwa province, said.
The federal government has termed the latest attacks "abominable".
"It's absolutely abominable and everybody has condemned the attacks, and across Pakistan the sentiment cuts across the entire political spectrum," Shahnaz Wazir Ali, the prime minister's advisor on polio eradication, told Al Jazeera.
"When men and women step out onto the streets to protect the lives of children ... why is it that it has become such a difficult and arduous task, and in fact a life-threatening mission now?"
She said that the distrust of polio vaccines was no longer widespread, due to extensive outreach campaigns undertaken by the government and international agencies to dispels myths about the medicine.
'Cruel and senseless'
Ban Ki-moon, the UN secretary-general, termed the killings "cruel, senseless and inexcusable" during a speech on Wednesday.
UNICEF and WHO issued a joint statement condemning the violence and pledging to continue the fight against polio in Pakistan.
"Such attacks deprive children in Pakistan of their right to basic life-saving health interventions and place them at risk for a disease that causes lifelong disability," the statement said.
Efforts to tackle the highly infectious disease in Pakistan have been hampered over the years by local suspicion about vaccination.
All of the victims were Pakistanis who were working with a UN-backed programme to eradicate polio, a disease that attacks the nervous system and can cause permanent paralysis within hours of infection.
The disease has been wiped out in all but a handful of countries. At least 35 children in Pakistan have been infected this year.