A criminal investigation has been launched into an "unauthorised" training exercise in which a policeman was accidentally shot by a colleague in Baħar iċ-Ċagħaq on Friday.

Sources have told The Times that the exercise, involving six policemen from the Mobile Squad, was organised by a police sergeant who recently attended a course in law enforcement run by the US Naval Criminal Investigative Service.

He took five of his colleagues to the desolate White Rocks Complex at about 3 p.m. to "show them what he had learnt".

But at the time, the policemen were all on duty and the three police cars they drove had been pulled from their routine patrols without official authorisation, the sources said.

They were practicing how to approach robbers inside a building at the dilapidated complex, which is often used by the army and police for such training, when a shot was fired and 41-year-old constable Peter Sammut was hit in the chest.

His colleagues gave him first aid until an ambulance arrived to take him to hospital, where he was found to be badly, but not critically, wounded. The colleague whose pistol had gone off, and who has not been in the force for long, was treated for severe shock.

The nine millimetre Glock 17, the officer was shot with, is a powerful pistol carried by the squad. It is one of the most widely used in law enforcement around the world because it is reliable, easy to use and takes more bullets than most other pistols. Sources said the accident is being taken very seriously by the police administration especially because the officers were on duty at the time.

The investigation is being conducted by the Criminal Investigations Department and Duty Magistrate Lawrence Quintano is carrying out an inquiry.

The last time a police officer was shot by a colleague was on December, 1983, when Constable Paul Zammit, 28, was killed in an accident at the shooting range at the Police Headquarters in Floriana.

He was a member of the Special Mobile Unit, which eventually became the Special Assignments Group.