According to the head of MI5, 2,000 or more people living in the UK can be considered a threat to the country's security through their backing of terrorism.
Jonathan Evans' comment was made during a speech at the yearly Society of Editors conference in Manchester, UK, on the 5th November 2007.
The figure announced is 20 per cent higher than Mr Evans had quoted 12 months ago.
Mr Evans described how those involved in work related to terrorism included children - some, aged just 15. Resources that might have been drawn upon to protect against terrorism were, instead, being deployed against the threat of foreign spies, he added.
Although it has been nearly twenty years since the Cold War formally ended, the number of Russian intelligence workers operating in this country is no less now than it was then, said Mr Evans.
"A number of countries continue to devote considerable time and energy trying to steal our sensitive technology on civilian and military projects, and trying to obtain political and economic intelligence at our expense", he stressed, adding that the fact that finance, technology and human resources were being continually injected into combating the threat was "a matter of some disappointment."
Mr Evans has now been at the helm of MI5 for some six months. At the conference, he explained how improved intelligence-assimilation in "extremist communities" had contributed to the increase in the number of terror suspects in the UK. However, he added: "...it is also because there remains a steady flow of new recruits to the extremist cause."
In expanding its support base, said Mr Evans, extremist groups were calculatedly targeting the young. Consequently, he urged for better measures to ensure their protection.
In respect of terrorism unleashed on the UK, he described the acts as "not simply random plots by disparate and fragmented groups", but components of a larger, "deliberate" al-Qaeda-led campaign.
Mr Evans emphasised how he did not believe the threat of terror against the UK had "reached its peak." He continued: "We will do our utmost to hold back the physical threat of attacks, but alone, this is merely containment.
"Long-term resolution requires identifying and addressing the root causes of the problem", he concluded.
Source - Security International's Current Affairs Correspondent
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