Terror cells are "more than likely" operating in the region, testing the loyalty of Muslim "traitors" who serve in Britain's Armed Forces, according to a Midland academic.
Dr Steve Hewitt, a Birmingham University expert on security, intelligence and the war on terror, said the foiled plot for an Iraq-style beheading of a Muslim soldier was meant to send a clear message to the city's Asian communities.
Often captors have used pictures, broadcast on the internet or on television, to achieve maximum impact such as in the execution of Baghdad-based Briton Kenneth Bigley, who was beheaded in September 2004. Yesterday's arrests in Alum Rock, Edgbaston, Kingstanding and Sparkbrook, followed six months of surveillance which suggested a Muslim soldier was to be kidnapped and beheaded, and the execution broadcast.
Dr Hewitt said: "I believe the idea behind this kidnap plot was about getting publicity and sending out the message that Muslim 'brothers' should not be fighting for the UK.
"This was meant to test Muslim men's loyalty to their religion, and that to join any of the British armed forces would be to turn against their own. They would be regarded as traitors.
"Events in Iraq have obviously influenced this plot, as feelings among the Muslim community still run high over this issue, so British foreign policy – whether the Government likes it or not – does play a big part in this scenario.
"I think it's more than likely terror cells will be established anywhere that has a dense multi-cultural population, like Birmingham, Leeds, London and Manchester."
He added that police handling of terror suspects could be counter-productive and ran the risk of "creating terrorists where none existed before."
The shooting of Jean Charles de Menezes at Stockwell Tube station in July 2005, during a police surveillance operation after the July 7 bombings in London, had raised major concerns over how to handle terror suspects.
Dr Hewitt added: "The fact MI5 said the number of people under surveillance is growing sends out a clear message to those cells still operating under their radar, that they cannot hide forever. The way in which these raids have been carried out, both today and in the past, do run the risk of creating terrorists where none existed before, particularly in cases like Jean Charles de Menezes.
"If the police had hoped to stop speculation over these arrests they should have briefed the press in the morning, rather than wait until mid-afternoon to confirm what journalists already knew." Last night terror analyst Professor Paul Rogers, of the University of Bradford, said it would be crucial to establish whether the alleged abduction plan was an isolated one-off or part of a wider movement.
He said: "If this is established it would be a substantial departure for groups loosely linked to al Qaida in the West. The point is whether this alleged plan was encouraged by the wider al Qaida movement or a one-off, independent action." Prof Rogers said al Qaida operatives who carried out hostage-takings and murders in Iraq had been "virtually disowned" by the insurgency leadership in Iraq."
"If such a plot were to be targeted against an individual then it would be a very new development as far as Britain is concerned, but obviously worrying as far as the fear factor is concerned."