A mystery noise has been keeping people awake in Norwich.

Described as sounding like an air raid siren or alarm, the "weird mechanical sound" was reportedly heard in the city centre on Saturday night.

But may have been heard on previous evenings too.

With no obvious explanation for the source of the sound, the mystery has led to speculation online as to the what caused the noise.

One woman who reported hearing the sound on Saturday evening posed the question: "Does anyone know anything about the noise that is like an air raid siren?"

Others who also heard it described it the noise as "eerie", "mechanical, high pitched and repetitive", while someone else said it sounded like "industrial machinery".

After much speculation, one popular explanation for the source of the noise was roadworks on St Stephens Road and Ipswich Road.