Thousands of miles from suspected alien crash sites, the people of Portsmouth have good reason to consider themselves safe from the prying eyes of extra-terrestrials

But images shared by residents of what appears to be a UFO earlier this week suggest otherwise.

Hovering ominously in the dusk sky, the dark grey, disc-like object has sparked mystery among sceptics and space enthusiasts alike.

Mystery: Residents were baffled by the sighting of a grey disc-shaped UFO in Portsmouth on Tuesday night

And as weather experts rule out the possibility that the object was a cloud, the town has been left wondering just exactly what it was flying over its homes on Tuesday evening.

Johnny Blackwell from Southsea said: ‘I don’t believe in UFOs, but when I saw this I didn’t know what it was.

‘It didn’t look like a cloud, and it was moving very fast.

‘It was a grey, disc-like shape, which I know sounds like a stereotypical UFO, but that’s what it looked like.

‘I don’t know much about military aircraft, but this was very fast-moving and very odd to see,’ the 23-year-old added.

Another observer, who declined to be named, said: ‘My initial thought was it was an aeroplane, but it was just moving too quickly.

‘I was the only one that saw it but was quick enough to take the picture.

‘I definitely believe in UFOs and am very interested in science fiction, and often look up at the sky in the evening wondering if there is anything or anyone else out there.’

Twitter users shared their confusion online.

Josh Harcourt-Kelly wrote: ‘Watching the sky and saw what looked like a UFO! Starting to believe in what people have been saying.’

Accompanied with the hash-tag ‘#pompeyufo,’ another, writing under the name Meral, said: ‘What’s this I’m hearing about a UFO spotted over Portsmouth’.

The ‘fast-moving’ object appeared at around 7pm and appeared to some observes to be flying too quickly to be a plane or military aircraft

Experts dismissed claims that the object was a cloud, saying it was ‘nothing to do with the weather’.

Laura Young, from the Met Office, said: ‘After looking at the images, I can say the object is nothing to do with the weather.

‘There is no meteorological explanation for it. It’s not a cloud.’

Karen Masters, senior lecturer in the institute of cosmology and gravitation at The University of Portsmouth, added: ‘Given the pictures show a dark object against a daytime sky, it’s clearly not an astronomical object.

‘Many UFO sightings are the planet Venus, but this one can’t be that.’

Those fearing alien invasion can rest easy however as even if there is extra-terrestrial life somewhere in the galaxy, it is too far away to make contact with Earth, she added.

‘The distances in space are so vast that it’s just not possible for aliens to be visiting Earth, so any interpretation suggesting this is an alien spacecraft is clearly wrong.’