A vicious assault on three Film In the Parks organisers at a screening of Spiderman has led to the cancellation of future outdoor movies.

More than 100 people turned out to the free event in Bonny Banks Park, Bernwood Road, Barton, on July 19.

At the end of the film, which finished at 11pm, a group of 15 to 20 males attacked three members of staff who were contracted by the council to set up and run the show.

A Thames Valley Police spokesman said the assault was unprovoked. "It was a senseless and very violent attack, and the offenders will be dealt with severely," he added.

He urged anyone with information about the incident to call police on 01865 266333 or Crimestoppers anonymously on 0800 555 111 as soon as possible. One contractor, who was kicked and beaten to the ground and suffered severe bruising and cuts, received treatment from paramedics.

Two other members of staff from the same company also received kicks to the head and chest. One of them suffered broken ribs and needed treatment at the John Radcliffe Hospital, Oxford. Police were called and arrested two males but later released them without charge.

Oxford City Council leader Alex Hollingsworth, who represents Barton and Sandhills ward, said: "These people have brought shame on themselves and risk the good name of the decent people of Barton.

"I urge anyone who witnessed this incident to contact the police immediately.

"Witnesses saw men as old as 40 involved in this mindless attack on our staff.

"They are ruining these free events for families who come from across the city to enjoy them."

The victims are all in their 40s and work for Oxford Film and Video Makers.

None of them want to be identified.

The city council's events officer, Anna Dolan, who organisers the events and witnessed the attack, is now reviewing future Film in the Parks events to assess security arrangements for staff.

The Film in the Park event scheduled for July 26 in Wood Farm Recreation Ground, a showing of The Wild Thornberries, has been cancelled. The council is also considering cancelling the next Film in the Parks event on August 24, in Barton Recreation Ground.

Film In The Parks is part of the city council's Fun In The Parks summer season, which is sponsored by the Oxford Mail.

Weekly screenings begin in July and finish in September.