Rigby killer wrote extremist messages online for six months before attack

With growing numbers of British Muslims turning towards violence, MI5 and the police maintain that it is impossible for them to track every suspect . Photo / Thinkstock

One of the killers of Fusilier Lee Rigby posted extremist messages on social media websites for six months without the authorities being alerted, an investigation into the death of the soldier is expected to state today.

The fact that MI5 were unaware of Michael Adebolajo's postings until after the killing will boost the intelligence agencies' claims that they need more information from internet service providers.

The Intelligence and Security Committee's report will also confirm, it is believed, that MI5 attempted to recruit Adebolajo as an informant and had known about him for almost eight years,

But the MPs concluded that the security services could not have known, from the intelligence in their possession, that he and accomplice Michael Adebowale would go on to commit the murder outside Woolwich Barracks in South London in May last year.

With growing numbers of British Muslims turning towards violence, MI5 and the police maintain that it is impossible for them to track every suspect. Adebolajo, 29, and Adebowale, 22, the report is due to say, were not regarded as an immediate threat.

The ISC has analysed contacts between MI5 and Adebolajo and is said to have rejected claims by some of his associates that this pressure drove him towards the killing. The committee accepted that such contacts are justified in attempts to gather intelligence about terrorist networks.

The failure by the internet service provider to alert MI5 about Adebolajo's online messaging was not deliberate, say Whitehall sources, but it highlights the need for a new system to be put in place.

- Independent