The Al-Rahma Islamic Centre in Muswell Hill, north London, was burnt down early this morning and the Metropolitan police believe the fire may have been started deliberately.
Scotland Yard's counter-terrorism officers are investigating the suspected racially-motivated arson attack on the Somali community centre.
Officers have confirmed the letters "EDL", which stand for the right-wing English Defence League, were found sprayed on the two-storey building which partially collapsed as a result of the fire.
London Mayor Boris Johnson called the attack "cowardly and pathetic".
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Emergency services were called in and six fire crews battled the blaze for more than an hour.
Two nearby properties on Coppetts Road had to be evacuated.
One woman suffered shock and was treated at the scene, London Ambulance Service said.
"I have spoken to community leaders and assured them that a thorough investigation is being conducted.
"The safety of our communities is always our priority and we are consulting widely, offering our support and reassurance," said the local borough's chief superintendent, Adrian Usher.
"The Somali community is in fear. We are all shocked about what has happened and we strongly condemn the attack on the centre.
"As you can see, the situation is a very serious one indeed," Abubakar Ali, from the centre, said.
Faith Matters, a group which monitors anti-Muslim hatred, has been warning against the alarming rise of Islamophobic incidents in and around London since the attack on the 25-year-old soldier on May 22.