A British jihadist says the UK is afraid of the terror skills he has learnt after he posted images of what appear to be homemade bombs.
A Twitter account apparently belonging to Nasser Muthana, a 20-year-old medical student from Cardiff, posted an image of 15 devices yesterday alongside a chilling warning.
"So the UK is afraid I come back with the skills I gained," the post said.
In another post, he shared an image of what appeared to be a weapon taken from an enemy, adding: "Look what we found on this shi'i, glad tidings we'll make sure his head is detachable."
He describes himself as a "soldier of the Islamic State of Iraq" on his Twitter profile.
The posts come just weeks after he was filmed alongside his younger brother Aseel, Reyaad Khan, also from Cardiff, and Raqib Amin, from Aberdeen, in a video urging others to join Isis in the fight in Syria and Iraq.
Aseel, 17, told BBC Wales in an online conversation that he had no regrets about leaving the UK to fight, claiming he was "willing to die" for the cause.
The brothers' father, who says he was not aware of his sons involvement with the militant group, told ITV News that he wished he could convince his sons to return to the UK.
Ahmed Muthana said watching footage of his sons in the recruitment video made him cry.
Security was increased at UK airports today after the US requested tougher measures amid reports that terrorists are preparing on devices which could evade scanners.
Passengers were reassured that the heightened security would not cause significant disruption.