More than 80 French nationals are training with the Pakistan Taliban in the lawless north-west of the country, according to a militant commander, raising fears of a renewed campaign against Western targets.
Mohammed Merah, the man believed to have killed seven people in south-western France, was trained by al-Qaeda in Waziristan on the Pakistan-Afghanistan border, according to the French prosecutor.
His visits, thought to be in 2010 and 2011, highlight again Pakistan's reputation for jihadi tourism and raise the chilling prospect of more attacks.
A senior commander with the Tehreek-i-Taliban Pakistan (TTP), an al-Qaeda affiliated group that has its stronghold in North Waziristan, said militants were following the unfolding events in France.
"There are more than 80 persons belonging to France, mostly in North Waziristan but some in South Waziristan. Five of them left from here in January," he told The Daily Telegraph on condition of anonymity. He said he could not disclose their destinations or plans, but the TTP would claim responsibility when the time came. He added that they had not trained anyone by the name of Mehra but recruits often used multiple identities.
French intelligence sources said about 30 French fighters trained by the Taliban were believed to have taken part in attacks on Western forces in Afghanistan.
North Waziristan's tribal communities lie beyond the control of Islamabad and the region has long been viewed as a buffer against chaos and lawlessness in Afghanistan. While the Pakistan military has launched offensives against other areas of the restive tribal belt, North Waziristan has so far been spared for fear of provoking a deadly backlash.
Afghan fighters of the Haqqani network have their headquarters around its main town, Miranshah. They use the area as a springboard for attacks against international and Afghan troops on the other side of the border.
The group has close ties to al-Qaeda and the TTP, creating what analysts have described as a "militant nexus" where groups plot missions, share personnel and swap expertise in terrorist tactics.
Expert bombmakers shuttle from group to group dispensing training. As well as Pakistani jihadis, the terrorist training camps - in reality often nothing more than a compound with one or two brick-built houses - in the north-west of the country have attracted dozens of Western men intent on learning skills to take home. Two British men, Ibrahim Adam and Mohammed Azmer Khan, were reported killed in drone strikes in South Waziristan last year.
Faisal Shahzad, the Time Square bomber, is believed to have been trained by the TTP, one of many plots traced back to the region.
Authorities in Pakistan said they were unaware of any visits made by Mehra. "We are looking into the matter but it is a brand new name to us," said a senior security official, speaking on condition of anonymity.
Saifullah Mehsud, of the FATA Research Centre, said most foreign recruits were Pakistanis born in Europe or the US. But whatever their background, they would be carefully vetted.
"If he has contacts, a friend who can introduce him, someone who has done the training and can vouch for him, then someone like this can get training," he said.