Muslim groups fear a "wave of attacks" following the burning down of an Islamic centre in north London in a suspected hate crime.
Counter-terrorism police are investigating after the Somali Bravanese Welfare Association - also known as the Al-Rahma Islamic Centre - in Muswell Hill was destroyed by a fire in "suspicious circumstances".
Police confirmed that the letters EDL (English Defence League) were spray-painted on the walls of the building and are investigating any potential connection between the graffiti and the fire.
It is feared that the building was destroyed in the latest of a series of anti-Islamic attacks in the wake of the murder of Drummer Lee Rigby in Woolwich on 22 May.
The EDL has denied any involvement in the blaze. SpokesmanKevin Carroll said: "The EDL do not approve of any religious buildings being attacked."
Tommy Robinson, the leader of the EDL, has been on a "nationwide campaign" to condemn Muslims in the wake of Rigby's death.
Muslim groups fear there could "wave of attacks" against them and have called for police to take action.
Massoud Shadjareh, chairman of the Islamic Human Rights Commission (IHRC), said: "Muslims feel scared and it is completely understandable.
"Muslims have been physically attacked, mosques burnt down, cemeteries vandalised and social media is full of anti-Muslim hatred and violent threats.
"More needs to be done to protect the Muslim community."
Since Rigby's death, there have been more than 200 reports of hate assaults on Muslims and attacks on mosques, according to Faith Matters, an organisation that works to reduce extremism.
Farooq Murad, secretary general of the Muslim Council of Britain, said: "This is the latest in a series of attacks on Muslim institutions since the horrific murder of Drummer Lee Rigby. The British Muslim community came out in droves to condemn this murder, and it is despicable that Muslims should be held to account and suffer in this way.
"It is time for serious action against such crimes. We had fine and decisive words from our leaders condemning the actions of the English Defence League. Now we need a proper response from our police authorities."
Cowardly, pathetic and pointless
Borough chief supt Adrian Usher said: "The safety of our communities is always our priority and we are consulting widely, offering our support and reassurance. All communities can be confident that they have our support and I can be contacted personally to answer their concerns."
Usher added he had received messages of support from other communities, including Jewish and Christian communities, to pass on to the Somali community.
He said: "I have been astonished by the calm resolve that community leaders have displayed. Despite such a blow to the community, their focus has been on moving forward and how best they can bring the community together in a positive way."
Police said the Islamic centre on Coppetts Road was not used for prayers, but used to give children additional teaching after school, as well as religious and language studies to children from the area.
The mayor of London, Boris Johnson, described the alleged arson as a "cowardly, pathetic and utterly pointless" act.
He added: "There is no place in an open, tolerant and diverse city like London for hate, for prejudice, for violence.
"I would urge people to give the police the time and space to investigate this incident fully. I have no doubt the Met will bring those responsible to justice."
Conservative MP Theresa Villiers, for Chipping Barnet said: "This kind of hate crime is absolutely despicable.
"This is not just an attack on the Muslim community it is an attack on all of us and our values."