The two victims, a German in his 40s and a 38-year-old Italian, were taken on January 20 by four gunmen from a house in the Multan district, in the province of Punjab.

The aid workers were working for the German non-governmental organization Welthungerhilfe, which is running a project for flood victims in the nearby district of Muzaffar Garh.

'Soon, perhaps next week, a video of the prisoners will be released together with the demands,' said a Taliban source who requested anonymity.

'Our brothers in Punjab took them and safely moved them to South Waziristan from where they were transported to North Waziristan,' said a rebel commander who also spoke on condition of anonymity. 'They are with Hakimullah Mehsud group now.'

Mehsud is the head of Tehrik-e-Taliban, an umbrella organization of more than a dozen militant groups.

He is also believed to be holding a Swiss couple - Olivier David Och, 31, and Daniela Widmer, 28 - seized by gunmen on July 1 as they were passing through the south-western province of Baluchistan on their way from India to Iran and Turkey.

The insurgents released videos of the couple in September and demanded ransom and the release of prisoners for their return.