Masked gunmen kidnapped a six-member polio vaccination team -- a doctor, two local employees of the World Health Organisation (WHO) and three guards -- in northwest Pakistan, an official said.
Local administration official Niamat Ullah Khan said the team was seized some 300 kilometres (190 miles) southwest of Peshawar, in Ping village at the border of South Waziristan.
A local official of the WHO in Peshawar confirmed the incident.
The kidnapping is the latest setback to efforts to eradicate the disease in Pakistan, and followed a bombing on Sunday targeting a polio team in Peshawar which killed a policeman.
Pakistan is one of only three countries in the world where the crippling virus is still endemic, along with Afghanistan and Nigeria.
Peshawar is considered "the largest polio virus reservoir of the world" by the WHO.
Nobody has claimed responsibility for the kidnapping so far. But militant groups see vaccination campaigns as a cover for espionage, and there are also long-running rumours about polio drops causing infertility.
More than 40 people, including health workers and police guarding the teams which administer polio drops to children, have been killed in Pakistan since December 2012.
A new campaign around Peshawar, which started early this month, will continue until April.
It sees teams go door-to-door every Sunday across the city to administer vaccinations to children for various diseases including polio, tuberculosis, tetanus, whooping cough, measles and hepatitis.
According to the WHO, Pakistan recorded 91 cases of polio last year, up from 58 in 2012. Victims are left dead, paralysed or with withered limbs.
Pakistan's failure to defeat polio stands in stark contrast to its neighbour and great rival India, which recently celebrated the eradication of polio three years after its last case.
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