Detective Superintendent Helen Millichap of Newham Police described the attack on the 16 year-old as "really unusual". She hopes the attacker will quickly be identified.
More top news
London and the worlds has united on Twitter in defiance of the attacks #prayforlondon #wearenotafraid
London was today a city of sirens and half mast flags in the wake of another terror attack.
MPs said they would "carry on" and go to work "as usual" in defiance of the terrorist attack outside the Palace of Westminster.