'Tragedy has touched the hearts of the British people'
Community and religious leaders say the small number of Islamic activists are endangering and embarrassing ordinary Muslims by supporting the atrocities.
They say the overwhelming majority of the two million Muslims living in the UK do not share the activist's extreme views.
Those views have horrified ordinary Muslims in the UK, said the spokesman for the Muslim Council for Britain, Inayat Bunglawala.
"These men are totally unrepresentative of British Muslims," he told BBC News Online.
"They have no grassroots support and could only muster a few hundred supporters out of a Muslim community of over two million in the UK.
"We must put them and their supporters into context. There are 800 mosques in Britain, which gives you an indication of how small their support is."
'Clowns'
He said the clerics were usually viewed as "clowns" by most Muslims, but in the current atmosphere they were considered extremely dangerous.
"Usually we try to ignore these groups and hope that they hang themselves with their own rope," said Mr Bunglawala.
"But we have been forced to issue a public condemnation of them this time because they are endangering and embarrassing ordinary Muslims.
'Extremely dangerous'
"We have been receiving hate mail, mosques have been attacked and now Muslims are being physically attacked."
He urged the media to stop giving extremist groups a platform to express their views.
"No major newspaper would give the BNP as much coverage as Labour or the Conservatives," he said.
"They are getting far more coverage than they warrant."
His views were backed by the principle of the Muslim College and former Imam of the London Mosque, Dr Zaki Badawi.
"These people do not represent the Muslim community," he said.
"In normal times they are just harmless lunatics but in times like these they are extremely dangerous."
A spokesman for Regents Park Mosque in west London told BBC News Online that the groups were a "very small minority".
Home Secretary David Blunkett announced this week that he is monitoring the activities of the Al Muhajiroun group. He is investigating its comments in support of the terror attacks.
He also said the vast majority of Muslims in the UK were appalled at the language used by group, fearing it could provoke a backlash against them.