The BBC has apologised for any offence caused by the inaccurate tweets, which generated speculation on social media about the state of the Queen’s health.
The tweets were posted on the day the corporation held a technical rehearsal for its future coverage of the Queen’s obituary - but the BBC stressed that tweeting was not part of the exercise.
By coincidence, the Queen was at hospital earlier today for her routine annual medical check-up.
Buckingham Palace took the unusual step of confirming the private medical visit after concerns were raised about her wellbeing following the tweet.
The messages were posted on Twitter from the account of BBC broadcast journalist Ahmen Khawaja, and it is understood she will now face disciplinary proceedings.
It said: “Breaking: Queen Elizabeth is being treated at King Edward VII Hospital in London. Statement due shortly.”
Prior to that, she had tweeted a short message saying the Queen had died.
The journalist later deleted the tweets, apologised for what she described as a “false alarm”, and suggested her phone might have been hacked.
Ms Khawaja tweeted: “Phone left unattended at home. Silly prank. Apologies for upsetting anyone!”
It is thought the messages might have been posted on Twitter by someone who thought the BBC’s rehearsal was a real event.
After speculation began to mount about the Queen, a Buckingham Palace spokesman said: “I can confirm that the Queen this morning attended her annual medical check-up at the King Edward VII’s Hospital in London.
“This was a routine, pre-scheduled appointment. The Queen has now left hospital.”
The BBC apologised for the tweet, which it said had been posted in error.
It said in a statement: “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.”