By Frank Gardner
Security correspondent, BBC News
British counter-terrorism officials say they are watching closely for any increase in activity by radicalised extremists in the UK, following Israel's assault on Gaza.
That's a bad sign when moderate leaders suddenly feel, 'How can we push back against this?' That their work over the last two or three years has been undermined by events in the Middle East
Prominent British Muslims are warning the government anger among young Muslims over events in the Middle East is reaching dangerous levels.
Ed Husain, co-founder of think-tank the Quilliam Foundation, is a former Islamist and expert on radicalisation. He said years of work on promoting moderation were now at risk.
He said: "The first response I got from the events in Gaza... [was] from Muslims up and down the country telephoning, saying, 'How can we prevent terrorism from happening on our streets again? Anger is so widespread, anger is everywhere.'
"That's a bad sign when moderate leaders suddenly feel, 'How can we push back against this?' That their work over the last two or three years has been undermined by events in the Middle East."
Representatives from a number of British Muslim organisations have expressed their concern in an open letter to the Prime Minister Gordon Brown, urging him to take more visible action to stop the violence in Gaza.
They have contrasted what they see as Britain's low-key approach with the example of the French President Nicolas Sarkozy, who swiftly departed to the Middle East on an intensive round of shuttle diplomacy.
Publicly UK Muslim representatives are wary of voicing their fears of a violent backlash in Britain.
But privately they say there is such widespread Muslim frustration over world leaders' apparent inability to stop Palestinian civilians being killed they fear the seeds are being sown for another major attack like the London bombings of 2005.
The Foreign Office says it is responding to Muslim concerns by holding regular briefings on Britain's efforts to secure a lasting ceasefire, with Foreign Secretary David Miliband and others working flat out to secure international agreement at the UN.
Knowing many British Muslims may be unaware of these efforts, Foreign Office officials say there are plans to announce them shortly through British mosques.
Meanwhile a spokesman for the Community Security Trust (CST), a self-protection group for British Jews, told the BBC it was on heightened alert after threats were made to Jews worldwide.
Earlier this week painted slogans calling for the killing of Jews appeared in north London.
On Sunday night an attempt was made to set fire to a synagogue in Brondesbury, north London, and the police have stepped up patrols.
The spokesman said CST had taken the precaution of putting out advice for people to be wary of suspect packages, to check their CCTV cameras were working, and to be on the lookout for what he called "hostile surveillance" around buildings.