Shoppers and workers were told to stay indoors and away from the central London area amid fears a rogue gunman had been spotted.
However, the rumours began when a secret Scotland Yard training dossier on how to tackle a rogue gunman was somehow leaked to the microblogging site.
It appeared to be a live police commentary about an ongoing incident involving a man running amuck with a gun.
Users of Twitter quickly relayed the hoax information, claiming police had issued “official warnings” of the incident. Another user’s separate update about a photo-shoot added to confusion.
Workers were warned to stay inside amid claims armed officers were at the central London site searching for the gunman just before lunch. As the information went viral, the term “Oxford Circus” become one of the most searched terms on the site.
Scotland Yard were later forced to issue a statement disclosing that information about a routine training exercise had been leaked.
It is thought the exercise involved discussions about a scenario involving several gunmen in a crowded shopping centre. While no officers were deployed details were disclosed by email by some taking part before it was leaked.
Police are understood to be furious over the leak, which occurred just after 11.30am, with officers warning of the dangers of social networking sites such as Twitter and Facebook.
Sources confirmed that an investigation was underway as to how the information was leaked. Arrests could be made over the leak.
Training exercises involving possible terrorists threats are routinely undertaken by authorities. “For everyone’s protection we need to know how this happened,” one source told The Daily Telegraph.
Nicola Whitehead, one of the users who posted the first “tweets”, later apologised for sending out the wrong information.
“It seems that I was DREADFULLY misinformed by an 'OFFICIAL' source. Apologies,” she posted.
A Scotland spokesman said: “We can confirm that there has been no firearms incident in Oxford Street.
“It would appear that some information about a routine police training exercise being held today has inadvertently got into the public domain.”
“As part of that exercise, participants have been given a hypothetical written scenario which involved an armed incident on Oxford Street.”
He added: “We would like to reaffirm that this is a training exercise only.”
