A 50-strong crowd hurled bottles at police as they tried to prevent people storming a derelict site to hold an illegal rave.

A member of the public reported cars and a van entering the site at Pinebanks on School Lane, Thorpe St Andrew, Norwich, at 11.50pm last night.

As officers secured the building more people began to arrive, via Harvey Lane and White Farm Lane, becoming hostile towards the police.

Extra police and a police helicopter were brought in to deal with the 50-60 strong crowd.

Bottles were thrown at officers who were using shield lines to keep crowds contained and from entering the building where sound equipment had been seized.

Officers managed to hold off the crowd, which began to leave the site at around 1.20am, with people moving off into the residential area. Police continued to monitor their movements and the incident was brought under control within two hours.

At 12.34am, police turned to social media to discourage more people from arriving, tweeting: “thinking of attending a rave in #norwich? don’t bother it’s not happening! police at scene.”

An investigation has been launched and detectives will be interviewing 12 people who were arrested, currently held in custody at stations across the county, later today.

Chief Superintendent Bob Scully said: “This was a serious incident and while nearby residents would have been disturbed by police activity an illegal music event running throughout the night and into the early hours would have caused more impact on the local community.

“The action taken last night to shut down this event falls in line with our efforts to reduce serious anti-social behaviour and environmental damage caused by illegal and unlicensed events.”