The Woolwich bloodshed spurred concerns not only about violence by Islamic extremists, but also about attacks targeting Muslims by people angered by Rigby's killing.
In Kent, police arrested a man on suspicion of "racially aggravated criminal damage" at a religious building. And on Wednesday night in Essex, a man with two knives was arrested after throwing a smoke grenade at the Al Falah Braintree Islamic Center and demanding someone come outside to answer to the Woolwich slaying, said the mosque's secretary, Sikander Sleemy.
Members of the far-right English Defence League clashed with police late Wednesday, with a tweet from its official account touting that "it's fair to say that finally the country is waking up!:-) NO SURRENDER!"
"Don't listen to the Government cover ups, The lies about Islam being peaceful," read another EDL tweet Thursday.
Political and social commentator Mohammed Ansar appealed for "a sense of calm (and) perspective" after what he called "a really, really heinous act of, I would say, criminality, ... not terrorism."
"What we don't need are knee-jerk reactions ... to really ratchet up tensions and really stoke and inflame anxieties within communities," he told CNN.
Nearly 100 senior British imams together issued a statement sharply condemning the "sick and barbaric" killing, which they said had spurred "hate-fueled individuals" to attack mosques and Muslims. The group called for action and dialogue to prevent attacks by extremists of all ilks.
"We (urge) our fellow citizens not to be taken in the mindless rantings of the (few) extra extremists in our midst," they said. "We, the British people, are not so easily fooled; nor are we so easily divided."