More than 400 Pakistani parents have been jailed after they refused to allow their children to receive polio vaccinations.
A spokesperson for the district administration in Peshawar said that the 471 parents were arrested on grounds of endangering public security, Reuters reported.
Riaz Khan Mehsud, deputy commissioner of Peshawar, said: "We have decided to deal with the refusal cases with iron hands. Anyone who refuses will be sent to jail.
"We have decided to take it as a challenge and make sure that every child gets vaccinated."
Officials explained that some parents refuse the vaccinations because they are influenced by clerics who argue the vaccines are against Islam.
Others also believe that the vaccinations are part of a plot by Western countries to sterilise people.
Referring to the mass-arrest, Pervez Kamal, director of health for Khyber-Pakhtunkhwa region in the north west, said: "There was no other option. We have run so many awareness campaigns for the parents and general masses that there is no harm in the vaccine, but to no avail."
He added that authorities had issued warrants for more than 1,000 parents after identifying "chronic" refusal cases.
According to government's records, at least 60,000 children have missed the vaccination due to it being blocked by their parents since the beginning of 2015.
Mehsud said there had been more than 14,000 refusals alone in Peshawar.
Polio spread in Pakistan after the Taliban terrorists, which control some areas of the country and aim to overthrow the current government, banned vaccinations. They have also been known to kill health workers.
Last November, four health workers were shot dead by armed motorcycle militants in Quetta, the capital of Balochistan province.
The militants have been targeting polio teams since US intelligence officials admitted they used the vaccination programmes to infiltrate the country and gather information on the whereabouts of al-Qaeda's then-leader Osama bin Laden in 2011.