Members of the public have reported 'suspicious' men hanging around Irvine Beach Park, North Ayrshire, apparently looking for people to meet up with despite the lockdown.
Litter including discarded jeans, tissues, condom wrappers and lubricant had been scattered in the area.
Police were called to the beach earlier this year when a woman walking her dog saw a man performing a sex act on himself, but no arrests were made.
Speaking on condition of anonymity, a worried resident said: "You see a lot of it going on down there, guys just hanging around suspicious.
"They were flouting the lockdown rules and still having sexual encounters in the woods on Marine Drive.
"The dirt mount was erected last week and has put a stop to the men parking up there.”
‘Unauthorised removal’ of sand
The local authority has taken steps to block off the area at the end of April in a bid to stop people parking up.
A North Ayrshire Council spokesman said: "We carried out the works to restrict off road motoring at the Beach Park.
"This was following unauthorised removal of sand to open up the area for access for illegal off-road vehicle activity.
"The area in question is also not a designated parking area, but rather an area of open space, which was being used for parking."
A spokesman for the Scottish Wildlife Trust said: "Wildlife reserves are tranquil places where people can connect with and enjoy nature.
"We strongly discourage any behaviour that causes offence or endangers the safety of other visitors.