PEOPLE who own BB guns, which fire small plastic balls, are being warned their realistic look may spark an unwarranted visit from the police Armed Response Unit.

BB guns can be bought easily and legally and are proving popular among teenagers say officers from Hertfordshire Constabulary.

But the realistic look has already sparked calls from concerned people reporting sighting of firearms, in areas such as Letchworth.

Police made the warning after armed officers came face to face with three youngsters who were carrying the guns which were made to look like semi-automatic handguns.

Sergeant Peter Knight of the Tactical Firearms unit, said: 'We must take reports of sightings of guns very seriously and this will involve the immediate dispatching of police officers.

'BB guns can look very realistic and in responding to such an incident, officers will treat the gun as being a real firearm until people have been searched or we have information to the contrary.'

He added: 'We want people who own imitation firearms to be fully aware of the consequences of showing them in public. We obviously do not want to cause unnecessary alarm to BB gun users by being approached by armed officers and additionally they should be aware of the distress they may cause to members of the public.'