Imran Khan, Al Jazeera's correspondent in Islamabad, said the Taliban had seized Khan in retaliation for the arrest by government officials of three of their fighters in Peshawar, the main city of the North West Frontier.
Muslim Khan, a Pakistani Taliban spokesman in Swat, earlier told the Reuters news agency: "He [Khan] is our guest. We have to discuss some issues with him. We will serve him tea and then free him."
The incident came as government negotiators try to extend the existing truce in the Swat valley which is due to end on Wednesday.
Maulana Fazlullah, a Taliban leader, denied his group agreed to lengthen the ceasefire after the government announced on Saturday it believed a truce agreement was imminent after agreeing sharia, or Islamic law, could be implemented in the region.
Fazlullah said pro-Taliban fighters in the Swat valley would only agree to extend the truce if the government introduced unspecified "practical steps".
"We heard that the government announced a permanent ceasefire, but we have announced a 10-day ceasefire and we will consider an extension when it ends," Fazlullah said.
While he did not specify which measures the group wants the government to implement, Fazlullah urged Islamabad to enforce sharia in the region and to create "an environment of confidence".
The new developments follow talks between local officials and a group headed by Maulana Sufi Mohammad, Fazlullah's father-in-law and the leader of the Tehrik-e-Nifaz Shariat Muhammadi movement, regarding the implementation of sharia [Islamic law] in the area around Swat.
Javed, the Malakand commissioner, said on Saturday that the pro-Taliban fighters had made a "commitment" to a ceasefire.
But Khan said that the details of the deal were still unclear and that the Taliban might want to act as the "enforcers" of sharia in Swat.
"The Taliban were trying to get the government to agree to their key demands including the implementation of sharia [and] the release of all Taliban prisoners," he said.
"But what they also wanted was to control [the implementation of] sharia law within the valley - that would mean a much tougher version of Islamic law than the one Sufi Mohammad had negotiated with the government."
Western powers, as well as many Pakistanis, have been alarmed by the government's offer to implement sharia in Swat in return for a ceasefire deal.
They fear a ceasefire could provide another sanctuary in Pakistan where al-Qaeda and Taliban fighters could move freely and that Taliban fighters elsewhere would be encouraged by the move.