This is why two black helicopters were flying over Leyland and South Ribble yesterday

Residents took to social media to share their images and videos, with the mysterious choppers not appearing on the Flight Radar tracking website.

But the Royal Air Force has now revealed that the Puma helicopters were actually circling parts of Lancashire to allow pilots and crewmen to complete essential training.

The helicopters are fitted with machine guns that might be visible to those on the ground, but the RAF has said these will not be carrying any live ammunition.

It said the weapons are 'general-purpose machine guns' and are operated by crew in the cabin for training purposes only.

The Puma helicopters are based at RAF Benson and will be operating at RAF Woodvale, near Formby in Merseyside, until Friday (July 10).

They will be flying between the hours of 8.30am and 6pm, but no night flying is expected.

This is what the RAF said about the helicopters

A spokesman for the Royal Air Force said: "Kuri Dawn is the final part of a training course that allows pilots and crewmen to operate the Puma helicopters on military operations within the UK and when deployed overseas.

"This is essential training providing key skills that will be required when they graduate from the Operational Conversion Unit and are posted to a front-line helicopter squadron.

"The operational phase of the course is the culmination of months of training by the six students and, all being well, will see them return to RAF Benson ready to graduate.

"At times, the helicopters will be operating in pairs and training in urban environments, both of which are key skills the crews require when deployed to Afghanistan in support of Operation Toral, as well as fulfilling National standby commitments in the UK.

"RAF Woodvale provides an excellent forward operating base for the Puma Force.

"It also provides additional support to the training being undertaken by introducing the crews to operating in unfamiliar surroundings and a different environment."