Two potential raves in the Powys countryside were thwarted by police after they received tip-offs over the Easter weekend.

In the first incident a resident in Gwynne Fawr, near Crickhowell, alerted officers from Dyfed-Powys Police about five vehicles suddenly arriving in the valley. These were quickly dispersed with the help of officers from Gwent police who also attended the scene.

In the second incident police swooped on 14 vehicles that had gathered near Talybont-on-Usk reservoir after a report was sent in by a Welsh Water Ranger.

Police forced the revellers to pack away their sound system and a number of them were forced to stay in a lay-by next to the reservoir because they were thought to be too drunk to drive.

It came as Operation Flamenco – a joint operation involving the two police forces, local authorities, Natural Resources Wales, Brecon Beacons National Park and support services firm LandMarc – swung into action.

Over the bank holiday weekend 23 potential sites were patrolled across Carmarthenshire, Ceredigion, Pembrokeshire and Powys.

As part of #OpFlamenco, police urged members of the public to report suspicious activity immediately, so gatherings could be disrupted before they had the chance to grow.

An event in the Brechfa forestry, Carmarthenshire, was also thwarted when Natural Resources Wales staff spotted a suspicious bag of stones, and ribbons tied to gates and hedges, designed as a signpost for revellers. Police seized the items and the gathering was cancelled.

On Twitter, PS 298 Owen Dillon said: “Dispersed a small gathering at the Talybont-on-Usk reservoir after call from @DwrCymru then turned vehicles back from Gwynne Fawr assisted by @gwentpolice to disrupt their plans. Officers left to cover the road. #OpFlamenco.”

In a tweet, Temporary Deputy Chief Constable of Dyfed-Powys Police, Claire Parmenter, thanked the police officers and staff who worked on the operation, saying: “Thank you to all the Dyfed-Powys Police officers and staff that have worked over the Easter break, some excellent proactivity and several illegal raves prevented through partnership working and intelligence sharing, diolch.”

Dai Rees, land management team leader from Natural Resources Wales, said: “Our forests and countryside should be available for everyone to enjoy but illegal raves can damage the environment, impact on wildlife and leave it in a dangerous state for other people.

“These events cause misery for visitors and local communities, and we’re already taking measures to make it more difficult for people to organise them on our land. But spotting the signs early and reporting them is also really important and means that we can take action early to stop large gatherings forming.

“Working together with the Police and local communities has proved invaluable and we continue to encourage people to report anything suspicious to the Police on 101.”

A Dyfed-Powys Police force spokeswoman said that efforts to crack down on raves would continue through the coming months, with “partnership members” working to tackle issues around unlicensed events, such as safety concerns when people take drink and drugs with no first aid or medical facilities to hand; inaccessibility of sites for the emergency services; the risk of drink and drug driving and rubbish being left at sites; the danger of fires and possible criminal activity such as underage drinking and drug dealing.

The public are being warned to look out for signs that a rave may be being planned and to call 101 if they see unusual numbers of vehicles, especially camper vans, vans or trucks, in remote countryside areas.

Other signs #OpFlamenco says to look out for include trespassers “recceing” sites in advance of a possible rave; people approaching landowners and asking to hire land for acceptable activities such as gymkhanas or scout camps.

For more information about how to look out for signs of an illegal rave visit #OpFlamenco on Twitter.