Police will patrol key Islamic institutions around the clock after children had to leave a boarding school during a suspected arson attack.

Sir Bernard Hogan-Howe, the Metropolitan Police commissioner, spoke last night of “difficult times for London’s communities” after the principal of the Darul Uloom Islamic School in Chislehurst, southeast London, said that intruders had set fire to the building.

A total of 128 pupils and staff fled the school at about 11.50pm on Saturday, and two males were treated at the scene for smoke inhalation. Firefighters took nearly an hour to bring the blaze under control but said damage was minimal.

Sir Bernard warned of elements in society which were attempting to drive a wedge between communities after the killing last month of Drummer