PESHAWAR, Pakistan — Pakistan has arrested 471 parents for refusing to vaccinate their children against polio amid persistent and violent opposition to the government's nationwide eradication efforts, officials said on Tuesday.

"There were chronic refusals and they were asking other parents as well to refuse polio drops to their children. This was the last option to arrest them," the police commissioner Peshawar police commissioner Riaz Khan Mehsud told NBC News.

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Pakistan is one of the last countries where polio, which has been eradicated in the West, is still endemic. The Taliban and some clerics in conservative and lawless strongholds in the northwest of the country have come out against the vaccinations, claiming they are part of a Western plot to sterilize children. Sixty-four people have been assassinated in the militants' drive to prevent vaccinations, according to Reuters, and health teams in parts of the country now only travel with armed guards.

"[The arrests were] the last resort as there was no other option. There is a lot of pressure on the local administration to tackle these refusals," said Pervez Kamal Khan, director general health services of Khyber Pakhtunkhwa government.

Opposition to the campaign gathered strength in 2011 when it emerged that Dr. Shakil Afridi, a Pakistani physician, ran a fake vaccination campaign in the garrison city of Abbottabad to collect DNA samples from al-Qaeda chief Osama bin Laden and his family to prove his presence there to the CIA.

IN-DEPTH

— Mushtaq Yusufzai

Reuters contributed to this report.