Image caption The incident happened at Nottinghamshire Police's headquarters at Sherwood Lodge, near Hucknall

A seven-year-old girl was injured when a police officer accidentally fired a gun in front of a group of children.

Nottinghamshire Police has launched an investigation following the incident at its headquarters last week, and has referred the matter to the Independent Police Complaints Commission.

The girl was hit in the face by an empty cartridge after a shot was fired into the ground, the force's commissioner said.

She did not need hospital treatment.

Paddy Tipping, Nottinghamshire Police and Crime Commissioner, said the girl was injured by the empty cartridge when it ejected from a gun fired into the ground on Thursday last week.

She suffered a "minor injury to her lip", police said.

The group of children and parents were being shown specialist police services including firearms and dogs at Sherwood Lodge, near Hucknall, after they won a local prize, he said.

"I am shocked, concerned and alarmed," he added. "This is a very serious incident and I have discussed it at length with the Chief Constable. I have received assurances it will never happen again."

The officer involved was a fully-trained firearms officer, Mr Tipping said, but was not currently on firearms duties, pending the outcome of the investigation.

No further details on the firearm have been revealed. The girl's parents, who were with her at the time, have been in regular contact with the Chief Constable.

Assistant Chief Constable Simon Torr said: "We are conducting a thorough inquiry to determine exactly how this unfortunate incident happened and have also referred the matter to the Independent Police Complaints Commission.

"We have spoken to the parents who were visiting force headquarters with their children to explain what happened and have apologised for any distress caused."

A Police Federation representative confirmed they were supporting the officer involved but could not comment any further at this stage.