The Met Police received reports of a vehicle being driven into a house in Hainault and "there were reports people have been stabbed".
"We understand the suspect went on to attack other members of the public and two police officers," the force said.
Footage shared on social media showed a man with a long knife in Laing Close.
A 36-year-old man was arrested at the scene and is in custody after the vehicle was driven into a property in the Thurlow Gardens area, police said.
"We are awaiting an update on the condition of those injured," the force added.
Transport for London (TfL) says Hainault London Underground station is closed.
Wes Streeting, MP for Ilford North, wrote on X, formerly Twitter: "A critical incident has been declared in Hainault."
He added: "There are station and road closures in place.
"The police, ambulance service and fire brigade are responding.
"I would urge people not to speculate until details are confirmed or post footage on social media."
MNA/PR
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