A British documentary film-maker has gone missing after setting out to interview Taliban leaders in Pakistan's lawless tribal area.
Two former senior members of Pakistan's intelligence agency, who were acting as guides, are believed to have been abducted at the same time.
Asad Qureshi was making a film in North Waziristan, the most dangerous tract of the tribal belt that borders Afghanistan. There were unconfirmed reports that a second Briton was working in the team.
One of the missing former officials from Pakistan's Inter-Services Intelligence (ISI) is Colonel Imam, the officer credited with creating the Taliban in the 1990s.
Pakistani military offensives have cleared most of the tribal zone of Islamist militants but North Waziristan remains a stronghold for the Taliban and al-Qaida and a continuing source of anxiety for western governments.
Qureshi is a British national of Pakistani descent and an experienced film-maker. He has been working as a freelancer since moving to Pakistan five years ago. He has made previous trips into extremist-held areas in Waziristan.
According to a former member of the Pakistani parliament, with whom the team stayed en route at the edge of the tribal area, there were two British nationals working on the film.
"Both had British passports," Javed Ibrahim Paracha said. The team stayed in his house in the town of Kohat on the night of 25 March. "They could have been picked up by American agencies or the Taliban." Paracha said they planned to visit the main town of Miram Shah the next day, but it is not known how far they travelled. The Foreign Office said it was not aware of the presence of a second Briton.
Travelling with Qureshi were two well-known former Pakistani intelligence agents, who have long-established links with militants. Retired ISI brigadier Colonel Imam, whose real name is Sultan Amir Tarar, and former ISI official Khalid Khawaja both worked with the mujahideen resistance to the Soviet invasion of Afghanistan, in the 1980s.
A Foreign Office spokeswoman said: "Officials at the British High Commission in Islamabad are urgently investigating reports that a British national is missing."