In a statement, the Metropolitan Police said senior national coordinator for counter terrorism policing, deputy assistant commissioner Dean Haydon, had formally declared the incident as terrorism.
The early investigation has revealed “a potential motivation linked to Islamist extremism”, the force said.
A 25-year-old man arrested at the scene on suspicion of murder is currently in custody at an Essex police station.
As part of the investigation, officers are currently carrying out searches at two addresses in the London area, the Met said.
The force believe the man acted alone and are not seeking anyone else in connection with the matter at this time but inquiries into the circumstances of the incident are continuing.
This article originally appeared on HuffPost UK and has been updated.Internet Explorer Channel Network