Armed men have kidnapped 11 Pakistani teachers in the country's northwest involved in a polio vaccination campaign for school children, according to officials.
Saturday's incident is the latest in a string of attacks on health workers trying to eradicate the deadly disease.
The teachers were taken from the private Hira Public School in the Bara area of the Khyber tribal agency, one of the semi-autonomous tribal areas along border with the Afghanistan.
Armed groups frequently attack polio vaccination workers in Pakistan.
They accuse the volunteers of being Western spies or part of a plot to sterilise Muslims.
One armed group leader said he would only allow vaccinations in his area if US drone strikes stopped.
The kidnappings came as Imran Khan, the opposition politician whose party controls Khyber Pakhtunkhwa province, gave Nawaz Sharif, Pakistan's prime minister, until November 23 to stop the US drone programme or he would order the closure of NATO supply routes in the province.
The kidnappers arrived at the Hira Public School on Saturday just after teams administering the polio vaccines had left, officials said.
Khyali Gul, a local official, said the attackers seized the teachers to an area controlled by Mangal Bagh and his Taliban-affiliated Lashkar-e-Islam group.
"Mangal Bagh and his men are opposing polio vaccination for children and don't allow teams to immunise children in their areas," Gul said.
Another Khyber official, speaking on condition of anonymity, said the teachers had been taken to an area where security forces cannot enter due to presence of fighters.
It was expected they would be released following negotiations with local elders, the official said.
A global eradication campaign has reduced polio cases by 99.9 per cent in the last three decades, but it remains endemic in Nigeria, Afghanistan and Pakistan.