- 2 updates
MI5 director general Jonathan Evans also warned that some terrorist groups would be considering whether they could launch an attack on Britain during this summer's Olympic games.
He insisted the Games were not an easy target, but added that there was "no such thing as guaranteed security".
All leave has been suspended at MI5 to ensure the service has its full complement of some 3,800 staff for the Olympics, double the number it had a decade ago after the September 11 terror attacks.
Latest ITV News reports
The head of MI5 made a rare public speech warning that Britons are increasingly heading to the Middle East to train as terrorists.