A large group of travellers have pitched up on Martello Fields in Seaford, the town council has said.
Residents are being urged to report any criminal or anti-social activity from the site to the police.
A spokesman said: “Seaford Town Council is aware that a large group of travellers have entered the Martello Fields without permission.
“The town council took the precaution of checking all the locks on the fields this morning and photographed them all as being fully locked.
“Criminal damage has therefore been reported to the police. However, to enable the town council to evict the trespassers as soon as possible residents are asked to report any criminal or anti-social activity from the site direct to the police.
“Photographs and videos are particularly useful. Once sufficient criminal activity has been recorded it is possible to evict them expeditiously.”
Residents can report any incidents to Sussex Police by phoning 101.
Alternatively they can report online at www.sussex.police.uk/ro/report.