Three spectators were injured when a door fell off an airborne Royal Air Force helicopter at an international air show.

Eyewitnesses at the show in Salthill, Galway, in the west of Ireland, said the Merlin helicopter based in 28 Squadron at RAF Benson, near Wallingford, was hovering about 100ft over a seaside hotel when a side door fell off and plunged into a large crowd below.

The Ministry of Defence (MoD) said it will launch an investigation into the circumstances surrounding yesterday's incident.

"We regret any injuries that were caused and an inquiry will take place to establish what happened," said an MoD spokeswoman.

The three injured spectators were taken to University College Hospital Galway where they are said to be in a stable condition.

None of the injuries are believed to be life-threatening.

Liam McBurney, a photographer who was capturing the event from the top of a hotel, said panic erupted as around 100 people scattered from the shoreline.

"The door fell off and was just like a piece of paper floating in the wind," he said.

"It floated over the promenade and crashed into the beach before bouncing about five to ten feet into the air and landing again."

Mr McBurney said the air show had just finished and the area was thronged with people when the incident happened.

He said the pilot of the EH Industries Merlin HC3 appeared to be attempting a manoeuvre over a hotel and towards the beach when the door ripped free.