Image caption More than 1,000 went to an illegal rave in Carmarthenshire in 2018

Police have warned of a crackdown on illegal raves over the bank holiday weekend.

Dyfed-Powys Police launched Operation Flamenco to prevent the gatherings in mid and west Wales, which can threaten wildlife and damage the environment.

Officers said they prevented three over the early May bank holiday weekend and have asked people to report anything suspicious.

Signs can be as subtle as a pile of stones or a ribbon tied to a tree.

Police said news often spreads quickly on social media, attracting people to remote rural locations - but the aftermath can last years.

Illegal raves can continue for days at a time, cause disruption for people living nearby, threaten wildlife and damage farmland and forestry.

Officers said large crowds of people - often under the influence of drink and drugs - bring a risk of fires and of litter being left behind.

Dai Rees, a team leader with Natural Resources Wales working with police to prevent raves said: "It's the mess left behind.

"This ranges from gas cylinders, human waste, glass - we have to clean up afterwards often at considerable cost.

Image caption Some of the mess left at the site of a rave

"These forests are open to the public - I wouldn't want to bring my children here and worry about what they're going to step on or see.

"It's also the peace and tranquillity of places like this. It's also prime nesting season for a number of birds, some very rare and if they're disturbed, it can cause the nest to fail."

Messages on social media promoting these events can also be coded, making it difficult to gather intelligence.

Sgt Owen Dillon, the lead officer on Operation Flamenco, said: "These raves often happen on a Saturday night, and the following day when we're trying to move people on they're still under the influence of drugs or alcohol and they're trying to get onto the roads.

"We have a duty of care to the people themselves but also to the safety of other people on the roads.

"And it's not just the big raves that are a problem, smaller gatherings of 20 or 30 vehicles also bring the same problems."