FARMERS and landowners have been warned by police to be on alert for people using their land for rave events.

Dyfed Powys Police and Gwent Police have issued the joint warning and say gatherings such as what they called "illegal raves" can cause "considerable anxiety to the community".

The forces also urged the public to be vigilant of people who approach landowners inquiring about using the land for what they termed "apparently acceptable activities such as gymkhana and Scouts/Guides events".

Chief Inspector Matt Scrase, of Dyfed Powys Police, said: "There is little doubt that these type of events are very well planned, organised and that local knowledge is important in drawing down the main group to a particular ’vulnerable’ field, or area of land which has been targeted previously as a suitable venue.

"Farmers, landowners and local communities are encouraged to report any suspicious activity immediately to the police; this may be an unusual numbers of vehicles, especially camper vans, vans or trucks in the locality, illegal trespassers who may be doing ‘recce’ of sites in advance of the event.

"I can assure local communities that police will take the appropriate action to deter illegal gatherings and deal robustly with any criminal offences discovered or disclosed."

Police say social networking sites have made it easier for organisers to spread the word of events and numbers attending could quickly grow.

A police statement said: "Members of the public are also urged to be vigilant of persons who approach landowners or enquiring for land, in the guise of hiring for apparently acceptable activities such as gymkhanas and Scouts/Guides events."

Suspicious activity can be reported to the police on 101.