Ahmen Khawaja, a reporter for BBC Urdu, sent out a tweet saying: "Queen Elizabrth [sic] has died."
Another tweet from the account of Khawaja said: "BREAKING: Queen Elizabeth is being treated at King Edward 7th Hospital in London.Statement due shortly: @BBCWorld."
The incident happened during one of the corporation's regular rehearsals for broadcasting the British monarch's obituary, which BBC bosses had asked staff to keep off social media.
"False alarm to Queen's death! She is being treated at King Edward 7th Hospital," she tweeted.
More From This Section
A BBC spokesperson said: "During a technical rehearsal for an obituary, tweets were mistakenly sent from the account of a BBC journalist saying that a member of the royal family had been taken ill.
"The tweets were swiftly deleted and we apologise for any offence."
Buckingham Palace, too, was forced to take the unusual step of issuing a statement reassuring the British public that their 89-year-old Queen was in good health.
Coincidentally, the Queen attended a London hospital for a "routine" annual check-up.