Radical preacher Anjem Choudary has blamed the terrorist murder in Woolwich on David Cameron and Britain's actions in Afghanistan.
Choudary, who grew up in Woolwich, was responding to reports that the alleged beheading was perpetrated by Islamic terrorists shouting "Allahu Akbar" - God is great.
Choudary tweeted: "National news tell me that the man killed in Woolwich is apparently being treated as terrorist as the attackers were shouting Allahu Akbar.
"If they were Muslims killing a British soldier then the presence of British troops in Muslim land [Afghanistan] is surely a cause of insecurity in the UK."
Referring to his upbringing in the area, Choudary continued: "I went to Mulgrave School [situated just yards from where the attack took place] & I know that the Muslim community is a peaceful one. I wonder what could have motivated this attack in Woolwich?!
"I blame Cameron for his foreign policy against Islam & Muslims! If the British regime sends people to murder Muslims in Iraq/Afghanistan, then it is bound to cause instability in the UK, time to withdraw!"
Earlier, Boris Johnson said: "I know that Londoners from all communities have been here. This is a city of incredible resilience and courage, we will come through this."
Choudary has previously courted controversy by imploring British muslms to bin their poppies on the eve of Remembrance Day, and claimed Islamic vigilantes are battling to rid London of 'evil' drunks and prostitutes.
The preacher's remarks contrast sharply with those of the Muslim Council of Britain (MCB), which has condemned today's attack in the strongest possible terms.
In a statement, the MCB said the attack was a "barbaric act that has no place in Islam."