One of the portable sirens which were tested in Oxfordshire

The county is the first in the country to trial two portable sirens, which will alert communities of a natural disaster or a serious imminent threat.

The devices, which were tested on Wednesday, are stored in a metal box.

Oxfordshire County Council said the sirens are about keeping the public informed rather than causing a panic.

'Final warning'

The alarms can be used with a public address system to advise people on what action they should take in the event of a major incident.

John Kelly, the county council's emergency planning officer, said the idea of using the German manufactured devices came after the severe floods last year.

He said: "We felt we need to warn and inform the public slightly better.

"This (the sirens) is a final warning that it is really serious, particularly in flooding."

If the trials prove to be successful they could be used throughout the country.