Residents claimed to have seen bright flashing spheres in the skies near Louth, Lincolnshire, where the 290ft turbine was mangled in a mystery collision.

Ministry of Defence insiders have reportedly said the UFOs could be unmanned stealth bombers on test flights.

The black delta-wing craft, called Taranis, is understood to have been making test runs on the coastal bombing ranges at Donna Nook and North Coates, which are right next to the site of the wrecked wind turbine.

Taranis is about the same size as the Hawk jet trainers used by the Red Arrows at nearby RAF Scrampton - it is being developed by BAe Systems to deliver bombs in battlefields.

Some witnesses have said an octopus-shaped UFO was seen flying through the air hours before the turbine was destroyed.

One woman said she saw an object fly towards the wind farm, while others described the lights as being linked by "tentacles", leading locals to dub it the octopus UFO.

Dorothy Willows, who lives a mile and a half from the crash site, said: "The lights were moving across the sky towards the wind farm. Then I saw a low flying object. It was skimming across the sky towards the turbines"

Eric Goring, 61, told The Sun that he has had so many sightings that he began thinking aliens were trying to abduct him.

Speaking of one encounter in September, he said: "I saw one come from the fields. I almost walked under it as it was just hovering 200ft above me. I didn't want to go too near it as I was worried they might beam me up."

A Ministry of Defence insider said: "We have to log all reports of UFOs. But in virtually all the cases there is a simple explanation - and test flights are a common one."

More mundane theories for the cause of the damage – from a block of frozen urine dropped by a passing plane, to simple mechanical failure - have been suggested, but none has yet proved conclusive.

Other explanations for the incident include vandalism from teenagers, a Russian spy plane, or fireworks from a local's birthday party.

by:telegraph