The murder of a soldier in a London street has prompted a dramatic increase in attacks on British Muslims, amid a series of arrests linked to the backlash.
Faith Matters, an organisation that works to reduce extremism, said more than 160 incidents had been reported to its helpline since Drummer Lee Rigby's killing on Wednesday.
That compared to the average of four to eight cases a day reported to the group before the attack.
It came as three men were arrested by Northumbria Police ahead of an English Defence League march that took place on Saturday afternoon in Newcastle, for allegedly posting racist tweets.
They followed a series of arrests for comments related to the murder made on social media.
Fiyaz Mughal, from Faith Matters, told Sky News: "There's been a substantial spike (in reports of Islamophobia).
"They range from general abuse to visible Muslims on the street, to graffiti at mosques, through to a firebomb at a mosque.
"I guess in all of this scenario, the individuals who killed Lee said they wanted a war and we don't want to go down that route so we're asking for cool and calm heads."
Yvette Cooper, Shadow Home Secretary, added her voice to the calls for calm.
"Anyone who seeks to divide our communities is doing the work of the extremists they say they oppose," she said.
"Mindless acts of violence against any of our communities serve no one. Some people are trying to use the vile attack in Woolwich as an excuse for more hatred, violence, and extremism. We must not let them."
News of the increase in attacks on Muslims emerged after it was claimed MI5 tried to recruit suspect Michael Adebolajo as an informer.
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Sad that some people blame a whole community based on the actions of a few. This is getting really ugly.