"It’s baffled several people, including Johnny Blackwell, 23, of Trevor Road, Southsea. He 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 craft, but this was very fast-moving and very odd to see.’
Johnny, a student, said he saw the object at about 7pm on Tuesday.
And Lewis Rogers, 26, of The Seagulls, Lee-on-the-Solent, saw the object when he was visiting a friend in North End.
The animation director 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.’
Some people on Twitter said the UFO is a cloud, but weather experts have dismissed this.
Laura Young, from the Met Office, said: ‘After looking at the images, I can say the object is nothing to do with the weather. It is not meteorological and is not a cloud.’