One woman was killed and five others injured by a man with suspected mental health issues who went on the rampage with a knife in central London late on Wednesday, an attack police said could be linked to terrorism.
"The safety of all Londoners is my number one priority," Khan said in a statement.
"I urge all Londoners to remain calm and vigilant. Please report anything suspicious to the police. We all have a vital role to play as eyes and ears for our police and security services and in helping to ensure London is protected."